A fractured pipeline that spewed crude oil off the coast of California could have been leaking for a year, US investigators said Friday.
Tens of thousands of gallons of oil are feared to have leeched into waters that are home to whales, dolphins and otters since a leak was discovered last weekend.
Stretches of prime surfing coastline have been shuttered as clean-up crews raced to prevent the spoiling of beaches, and rescue animals caught up in the slick.
US news outlets reported that a ship's anchor could have been responsible for dragging the pipeline along the seabed and splitting it open.
But Coast Guard officials investigating the incident said Friday the rupture might not be new, and could have happened as long as a year ago.
Captain Jason Neubauer said multiple ships' anchors may have contributed to the displacement of the pipe, and it was not initially clear when the leak began.
Underwater video of the damaged pipeline shows "marine growth" around the 13-inch crack that is leaking oil -- something that would not have appeared overnight.
This discovery "has refocused the ... timeframe of our investigation to at least several months to a year ago," Neubauer said.
A routine inspection by pipeline owner Amplify Energy which took place last October showed no damage, he said.
"We're going to be looking at every vessel movement over that pipeline and every close encroachment over the past year," Neubauer said.
That will include examining satellite images, radio broadcasts and vessel traffic patterns.
The nearby container ports of Los Angeles and Long Beach are among the world's busiest.
A pandemic-sparked logjam has left dozens of huge vessels at a time anchored at sea while they await a berth.
Captains ordered to wait outside the port are given specific places to set anchor, but investigators will look to see if any anchors have been dropped in the wrong place.
They will also look to see if a storm that tore through the area in January could have moved any of the ships.
Martyn Willsher, the chief executive of Amplify Energy, said this week that underwater observations revealed that 4,000 feet (1,200 meters) of the pipeline were not where they should be.
"The pipeline has essentially been pulled like a bowstring," he told a press conference on Tuesday.
"At its widest point it is 105 feet away from where it was," he said, adding the break in the pipeline was at the apex of this bend.
Willsher refused to speculate on the cause of that displacement and whether a ship's anchor could be responsible, but said: "It is a 16-inch steel pipeline that's a half inch thick and covered in an inch of concrete.
"For it to be moved 105 feet is not common."
Officials involved in the clean up originally said well over 100,000 gallons of crude could have been spilled.
But on Thursday they said the actual amount could have been around 25,000 gallons.