A container ship, the Rotterdam Express, has come under suspicion as a possible culprit in the ruptured pipeline that leaked as much as 126,000 gallons of crude oil into the Pacific near Huntington Beach last week. And on Wednesday, investigators boarded the ship in Oakland, where it is now docked.

An investigation of ship location data from MarineTraffic by the Associated Press found that the Rotterdam Express made a number of odd movements in the days leading up to the spill, which was first detected on Friday. The data showed that the German-flagged ship had been assigned an anchorage known as SF-3, which is the closest to the pipeline rupture at about 2,000 feet, after it arrived outside the Port of Long Beach early on September 22.

On September 22 around 5 p.m., the ship's beacon indicated it moved thousands of feet to the southeast, directly over the oil pipeline. The ship then engaged its engines and moved back to its anchorage about 10 minutes later. This movement happened twice more, according to the data, once around midnight, and then again before 8 a.m. on September 23, each time shifting thousands of feet southeast, per the AP.

Large container ships can move in the wind, and the theory some experts are floating is that the Rotterdam Express moved with its 10-ton anchor down, and the anchor caught the pipeline and pulled it out of alignment. Divers investigating the pipeline say a 4,000-meter section was pulled "like a bow" as much as 105 feet from its original position at the widest point. Oil was seeping out of a crack in the pipeline.

As Steven Browne, a professor of marine transportation at California State University Maritime Academy, tells NPR, an improperly set anchor will drag "whatever the anchor gets fouled on" if tides and winds are strong enough.

Hapag-Lloyd, the owner of the Rotterdam Express, has denied that the ship was involved in the pipeline rupture, and they deny that the ship moved at all from its anchorage.

"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."

But Nikolas Xiros, a professor of marine engineering at the University of New Orleans, tells the AP it's highly unlikely that the transponder data seen on MarineTraffic would be off by a thousand feet or more.

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

As the Associated Press reports, the Rotterdam Express was anchored until Monday, when it entered the Port of Long Beach to unload. It then sailed for Oakland that day, and was scheduled to depart Wednesday night. But U.S. Coast Guard investigators boarded the ship Wednesday, and it remains in port.

A U.S. official confirmed to the AP that the Rotterdam Express had become a focus of the investigation, however this was still in its early stages.

Petty Officer Steve Strohmaier, a Coast Guard spokesperson, only told the AP that investigators were analyzing the Coast Guard's own electronic charting systems to determine which ships were in the area of the pipeline rupture last week.

In a statement to NPR, Congresswoman Katie Porter said, "We are going to make sure that we have answers as to how this happened, and to make sure that we hold the responsible party accountable." Porter, a Democrat, chairs the oversight and investigations subcommittee of the House Natural Resources Committee, and she also represents a district a few miles away from where the spill occurred.

Officials from Houston-based Amplify Energy, which owns the pipeline and three oil platforms in the Los Angeles area, have said that the pipe was cleared and no more oil was leaking from the pipe. Video taken by the Coast Guard on Monday showed the cracked section of pipe, and showed no visible oil coming out.

The amount of oil that escaped into the water is still not known.

Photo by Smith Collection/Gado/Getty Images