HUNTINGTON BEACH (AP/CBSLA) — A massive cargo ship made a series of unusual movements while anchored in the closest spot to an oil pipeline off the coast of Orange County that ruptured and sent tens of thousands of gallons of crude oil washing up on beaches, according to data collected by a marine navigation service.

An undated photo of the Rotterdam Express, a German cargo ship, that was in the area of the oil pipeline that ruptured off the coast of Huntington Beach, Calif. on Oct. 2, 2021. (Credit: Tony Alter)

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The pipeline leak, which was reported Saturday morning off Huntington Beach, may have spilled anywhere up to 144,000 gallons of oil into the ocean waters. The spill occurred in federal waters at the Elly rig, about 4 1/2 miles off-shore. The rig and pipeline are owned by Houston-based Amplify Energy.

Federal authorities confirmed Tuesday that a section of Amplify Energy’s oil pipeline was damaged and moved more than 100 feet along the ocean floor, an indication that a ship’s anchor may have caused the spill.

The Coast Guard is investigating whether the anchor of the Rotterdam Express, a German-flagged ship, might have snagged and bent the pipeline. Amplify Energy operates three offshore oil platforms off the O.C. coastline.

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The nearly 18-mile pipeline runs from Amplify Energy’s offshore drilling platforms to a pump station in Long Beach.

The Associated Press reviewed more than two weeks of data from MarineTraffic, a navigation service that tracks radio signals from transponders that broadcast the locations of ships and large boats every few minutes.

That data shows the Rotterdam Express, nearly 1,000-feet-long, was assigned to anchorage SF-3, the closest to where the pipeline ruptured. The ship made three unusual movements over two days that appear to put it over the pipeline.

In a statement to AP, Hapag-Lloyd, the shipping company that operates the Rotterdam Express, denied any role in the spill.

A U.S. official told the AP on Wednesday that the Rotterdam Express has become a focus of the spill investigation. The official cautioned the ship is only one lead being pursued in the investigation, which is in the early stages.

According to MarineTraffic data, the ship left Long Beach on Monday for the Port of Oakland, where it was moored at a dock Wednesday night. It departed the Port of Oakland on Thursday.

TIMELINE: Huntington Beach Oil Spill

The investigators are seeking to collect tracking and navigational information from the vessel that could help them identify its exact movements, the official said. They are also seeking preliminary interviews with at least some crew members.

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The official could not discuss the investigation publicly and spoke to the AP on condition of anonymity.

The MarineTraffic data shows the Rotterdam Express arrived outside the Port of Long Beach early on Sept. 22 and dropped anchor about 2,000 feet from the pipeline.

The following day, at about 5 p.m., the data for the ship’s locator beacon indicated that while anchored it suddenly moved thousands of feet to the southeast, a track that would have taken it over the pipeline lying on the seafloor about 100 feet below. The ship appears to have then engaged its engines to return to its anchorage about 10 minutes later.

The ship then moved again around midnight and a third time shortly before 8 a.m. on Sept. 23, each time moving back to its assigned anchorage, according to its online location data. The Rotterdam Express remained at spot SF-3 until Sunday, when it moved into the port to unload.

The first report of oil in the water near the pipeline were made Friday evening. A document obtained by CBS2 from the U.S. Department of Transportation indicates a low pressure alarm went off on the Elly at 2:30 a.m. Saturday. However, workers in the control room of Beta Offshore, a subsidiary of Amplify, did not shut down the pipeline until 6:01 a.m. Saturday, about 3 ½ hours later.

Amplify’s CEO Martyn Willsher said Tuesday divers determined a 4,000-feet section of the pipeline was dislodged 105 feet, bent back like the string on a bow. Oil escaped through a slender crack.

The amount is unclear. Amplify has said publicly that no more than 126,000 gallons leaked but told federal investigators it may be only 29,400 gallons.

Nils Haupt, a spokesman for Hapag-Lloyd at its headquarters in Hamburg, Germany, denied in an email Wednesday that the ship ever moved off anchor from spot SF-3 during that period. He said the transponder data displayed by MarineTraffic is erroneous.

“We have proof by the logbook, which is updated hourly, that the vessel did not move,” Haupt said. “MarineTraffic in this case is wrong and the position is indeed incorrect.”

In a statement to CBSLA Thursday, Hapag-Lloyd wrote:

“The Rotterdam Express has anchored at SF-3 anchorage off LAX-LGB area, as directed by San Pedro Traffic, on 21.09.2021, at 5:54 Local Time. The anchor was dropped exactly as requested and confirmed by San Pedro Traffic. During the period in question the vessel has not moved from anchorage and has not passed over the pipeline. During anchorage no oil in the water has been spotted. Hapag-Lloyd is fully cooperating with all authorities involved. I confirm that USCG has boarded the ship yesterday evening Central European Time.”

Nikolas Xiros, a professor of marine engineering at the University of New Orleans, said it would be highly unlikely that the transponder data for a ship, which works through a global network called the Automatic Identification System, would be off by several thousand feet.

“AIS transporters are very accurate and the whole system is also very accurate,” Xiros said after reviewing the location track for Rotterdam Express. “I think probably the ship moved, that’s what I think. And with the anchor down, which was a big problem.”

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(© Copyright 2021 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)