More than 12 hours passed after officials were notified of a sheen on the water off the coast of southern California before a response to the Huntington Beach oil spill began, records show. Questions are now arising over why the response took so long and how that might have intensified the ecological disaster taking form on the Orange county coastline.

The US Coast Guard said in a statement on Tuesday that the initial reports of a spill weren’t enough to warrant sending out boats to look for a leak.

Authorities say a pipeline that leaked tens of thousands of gallons oil into the water was split open and apparently dragged along the ocean floor. The coastguard captain Rebecca Ore said Tuesday that divers had determined about 4,000ft (1,219 meters) of the pipeline had been “laterally displaced” by about 105ft. She did not say what might have caused the displacement.

Roughly 126,000 gallons (476,961 liters) of heavy crude seeped into the ocean off Huntington Beach over the weekend, splattering the beaches with black. Coastal fisheries in the area are closed to commercial and recreational fishing, and the governor, Gavin Newsom, declared a state of emergency late on Monday. County prosecutors and federal agencies were considering charges and lawsuits.

Oil is no reportedly longer leaking from the pipeline but a cause has not yet been determined. Divers and remotely operated vehicles deployed by the coastguard to assess the source of the leak discovered a large section of the pipeline had been displaced. Investigators are looking into whether a ship’s anchor might have struck a pipeline on the ocean floor, coastguard officials said on Monday. Amid a global supply chain crisis, more ships are waiting offshore than usual to access California ports.

The pipeline connects to an offshore oil production platform named Elly, which is connected by a walkway to a drilling platform named Ellen. The platforms and another nearby platform are in federal waters and owned by the Houston-based company Amplify Energy Corp.

Before sand berms could be completed and booms – floating barriers that slow the spread and help contain spills – were deployed, the toxic oil washed into protected marshlands and endangered species’ habitats. Dead birds and fish were reported along the shore as animal rescue organizations rushed to the scene. So far, officials said, seven blackened birds had been recovered and were being cared for. A pelican, its feathers irreparably tarred, had to be euthanized.

It’s too early to fully assess the full ecological impact of the disaster but scientists with the California department of fish and wildlife are taking samples of the sea and sand. The area is expected to see an influx of migratory birds in the coming weeks, which could increase the toll.

“It is heartbreaking,” said John Villa, the executive director of the Huntington Beach Wetlands Conservancy, which operates three protected marshes. All of them have been affected. “You go through a whole lot of work and effort to buy the property and restore the wetlands,” he said. “You maintain it and try to keep it as pristine as possible – and then this happens.”

Crews with the Orange county public works department worked through the weekend to create a berm blocking more tarnished water from entering the preserve but by then some oil had already seeped through.

By Tuesday afternoon, roughly 4,788 gallons of oil had been removed from the water, according to officials, and 11,360ft of boom had been deployed to corral the slick. Roughly 15.7 miles of coastline was contaminated, according to the coastguard. Beaches in Huntington and Laguna were closed, along with Newport Harbor and Dana Point Harbor. It may be months before they are reopened.

It’s unclear how much damage could have been prevented if action had been taken sooner.

Martyn Willsher, CEO of Amplify Energy, the company that operates the rig, said at a news conference on Monday that the company discovered the spill on Saturday morning. Lt Cmdr Jeannie Shaye of the coastguard also said the agency hadn’t been notified of the disaster until Saturday. But state oil spill records reviewed by the Associated Press show that the spill was sighted on Friday evening.

A foreign ship anchored off the coast witnessed an “unknown sheen in the water near their vessel” at 6.13pm and the report was called into the response center just after 8.22pm, according to the state report. Lonnie Harrison Jr, vice-president of Colonial Compliance Systems, which works with foreign ships in US waters to report spills, said one its clients had reported the sighting.

About six hours after the first report was received, the National Oceanic and Atmospheric Administration reported that satellite imagery spotted a possible oil slick more than three miles (5km) long. The report by the National Response Center (NRC) noted that there had been many vessels nearby but none were clearly associated with the spill and that “prevented possible identification of a point source”. But, it continued, “the NRC report allows for high confidence that this was oil”.

In a press release on Tuesday, the Unified Command, which includes the coastguard, the state fish and wildlife department, and Amplify Energy wrote that reports like the one received on Friday evening were common and “in many cases, the sheen reported can be natural seepage of oil or sheen that is never located”.

Crews from the fish and wildlife deparment’s office of spill prevention and response went out to assess the situation before sunrise on Saturday, the press release states, but returned to shore due to foggy conditions. They deployed again when conditions improved, and soon after the company confirmed that oil had spilled from the pipeline.

Regulations enforced by federal and state institutions require rapid reporting after a spill. Oil companies have failed to comply in the past, leading to criminal prosecutions against Plains All American Pipeline, which caused a coastal spill near Santa Barbara in 2015, and Southern California Gas Co for a huge well blowout later that year.

Amplify platforms submitted a spill response plan in 2016, noting the requirement for immediate notification of federal officials when more than one barrel of oil is released into the water. The oil platform known as Elly was supposed to be equipped with an automated leak detection system that would sound an alarm whenever a change in the flow of oil is detected, alerting a control room staffed around the clock.

The Orange county district attorney, Todd Spitzer, is assessing whether state charges can be brought against the company even though the leak occurred in waters overseen by the US government. Other potential criminal investigations were being pursued by the US Department of Justice, the coastguard and the California department of fish and wildlife, officials said. A federal lawsuit has also been filed by Peter Moses Gutierrez Jr, who claims he was exposed to the contaminants that washed up on the beach.

Safety advocates have pushed for years for federal rules that would strengthen oil spill detection requirements and force companies to install valves that can automatically shut down the flow of crude in case of a leak. The oil and pipeline industries have resisted such requirements because of the high cost.

The US representative Mike Levin has introduced legislation to ban new leases for oil or natural gas development and production on the southern California coast. In his bill he notes that, along with threats to habitats and marine life, the area beaches are a boon for the local economy, accounting for roughly $42bn and 600,000 jobs from fishing, tourism, and recreation in San Diego and Orange counties. Those activities have also been threatened by the spill and the closures, which will likely stretch on for weeks.

• This article was amended on 8 October 2021 to correct the conversion from US gallons to liters.