TOKYO — Japanese authorities said Monday that they were almost finished with their investigation into last month’s collision between a Philippine freighter and a U.S. naval destroyer that left seven Navy sailors dead, but still haven’t been given access to data from the U.S. side.

The container ship, the ACX Crystal, and most of its crew were allowed to leave Japan for Thailand on Sunday after repairs were finished. Coast guard officials declined to give details.

A spokesman for the company that owns the freighter, Yoshinori Fukushima, said Monday that the captain and some crew members had stayed behind voluntarily for additional questioning.

The crash occurred on June 17 south of Tokyo off the Izu peninsula in an accident-prone area known for congestion with ships trying to reach Tokyo by daybreak. That is within Japanese territorial waters, but the U.S. military holds the right to investigate its naval vessel and has not cooperated with Japan’s investigation, which is allowed under the bilateral status of forces agreement, officials said.

Japanese coast guard officials said that they were still discussing possible cooperation with the U.S. side, but that nothing concrete has been decided and they could not say when a conclusion was expected.

A team of experts at the Japan Transport Safety Board is also investigating the cause of the accident. Katsunori Takahashi, a spokesman for the safety board, has said officials may have to compile a report of what caused the accident only with what information they have. There have been past cases in which the U.S. never cooperated, he said.

U.S. and Japanese officials haven’t said whether crew members from the USS Fitzgerald were thought to be responsible for the crash.

The USS Fitzgerald, by far the smaller vessel, was carrying nearly 300 crew members when the ships collided. Severe damage to the right side and bottom of the guided missile destroyer flooded the berths of 116 sailors. Navy divers found the bodies of seven sailors in the ship after it returned to the naval base at Yokosuka, near Tokyo.