(Elyse Samuels,Monica Akhtar/The Washington Post)

A U.S. Coast Guard investigative team arrived Monday in Japan to start piecing together the sequence of events that led to a deadly weekend collision between a Navy destroyer and a fully loaded container ship four times its size. 

There are now multiple investigations into the accident, by the U.S. Navy and Coast Guard as well as the Japanese Coast Guard and its Transport Safety Board. 

“The [U.S.] Coast Guard will be taking the lead in the marine casualty investigation,” said Lt. Scott Carr, spokesman for the U.S. investigative team. 

Investigators will be questioning the crew of the USS Fitzgerald, the Aegis guided-missile destroyer that collided with the ACX Crystal, a Philippine-flagged container ship, just off the Izu Peninsula. The crash site was south of the Fitzgerald’s home port, the 7th Fleet base at Yokosuka, and of Tokyo, where the Crystal was headed. 

Seven sailors died because of the collision, which severely damaged the berthing compartments where they were sleeping, resulting in flooding. The ship’s captain also was injured and was evacuated to the base hospital at Yokosuka. 

One of the seven sailors was identified Sunday night as 37-year-old Gary Rehm Jr. As rescuers searched for Rehm, a shipmate stayed on board the listing Fitzgerald and texted reports to his wife in the United States, Rehm’s mother-in-law told The Washington Post.

“She said she wasn’t leaving the ship until they found him,” Joan Braniff said. “They kicked her off, and she stayed on the pier until they found him.”

Now Erin Rehm is a widow. They had been married for nearly all of the fire controlman’s 19-year Navy service, Braniff said.

“You could tell right from the start he just adored her,” she said. They sang karaoke on a Play­Station in Hampton, Va., when he was home and talked many times each day when he was deployed. He had been serving on the Fitzgerald for nearly two years, according to the Navy.

“He was supposed to be coming home in September,” Braniff said.

And next year, she said, Rehm was planning to retire from the military and stay home for good.

The 20 crew members on the container ship, chartered by the Japanese shipping company Nippon Yusen, were reported to be unharmed. 

“We are working to gain access to the crew of the Philippine-flagged vessel, but it’s taking a little bit of time to make that happen,” Carr said. 

The collision appears to have happened at about 1:30 a.m. Saturday, not 2:30 a.m., as the 7th Fleet reported. That was the time when the Fitzgerald alerted the 7th Fleet of the collision, a spokesman said. 

The Japanese coast guard also changed its assessment of when the collision happened. It had initially said that the Crystal reported the collision at 2:25 a.m. and said it had occurred five minutes earlier.

But after interviewing the container ship’s crew, the coast guard said the collision happened at 1:30 a.m.

Yoshihito Nakamura, a spokesman for the Japanese coast guard, said the change in timing was not necessarily suspicious. Crews often give priority to responding to the emergency, he said, adding that the exact timeline would become clear during the investigation.

Marine tracking data showed the Crystal steaming west toward Tokyo, but shortly after 1:30 a.m. it performed a sudden U-turn and returned to where it had been. 

“We are fully cooperating with the investigation,” said Manami Meguro, a spokeswoman for Nippon Yusen. 

The ship unloaded some of its cargo at Tokyo, then continued to Yokohama, where it offloaded the rest of its containers. After that, it will likely be taken out of service while the investigation takes place, the newspaper Asahi Shimbun reported. 

Both Nippon Yusen and the ship’s owner, Kobe-based Dainichi-Invest Corp., declined to confirm the report.

Japanese investigators boarded the container ship over the weekend and interviewed the captain and crew, according to other local news reports. 

“In general, when two vessels collide, then both would be subject to investigation, and suspicions of endangering marine traffic through professional negligence could apply to both vessels,” said Nakamura, the coast guard spokesman. 

Three investigators from ­Japan’s Transport Safety Board have inspected the container ship inside and out, spokeswoman Yuko Watanabe said. It was not clear when or whether Japanese investigators would be able to check the Fitzgerald or talk to its crew, she said. 

The path of the Fitzgerald before the collision is not clear because military ships do not transmit location data like commercial vessels. 

The Fitzgerald is part of the same fleet as the USS Ronald Reagan aircraft carrier, also based at Yokosuka. The Reagan carrier group, as well as other groups, have been particularly active in the area around the Korean Peninsula in recent months because of heightened tensions with North Korea. However, the Fitzgerald was operating independently of the Reagan at the time of the collision. 

Avi Selk in Washington and Yuki Oda contributed to this report.