A US warship struck by a container vessel in Japanese waters failed to respond to warning signals or take evasive action before a collision that killed seven of its crew, according to a report of the incident by the Philippine cargo ship's captain.

Key points: The cargo ship's captain says the ACX Crystal signalled at the warship with flashing lights

The cargo ship's captain says the ACX Crystal signalled at the warship with flashing lights The report is the first detailed account from a party involved in the incident

The report is the first detailed account from a party involved in the incident The accident marked the greatest loss of life on a US Navy vessel in over a decade

Multiple US and Japanese investigations are underway into how guided missile destroyer USS Fitzgerald and the much larger ACX Crystal container ship collided in clear weather south of Tokyo Bay in the early hours of June 17.

In the first detailed account from one of those directly involved, the cargo ship's captain said the ACX Crystal had signalled with flashing lights after the Fitzgerald "suddenly" steamed onto a course to cross its path.

The container ship steered hard to starboard to avoid the warship, but hit the Fitzgerald 10 minutes later at 1:30am (local time), according to a copy of Captain Ronald Advincula's report to Japanese ship owner Dainichi Investment Corporation.

The US Navy declined to comment and it was not possible to independently verify the captain's account.

Indication no imminent collision alarm sounded

Sorry, this video has expired Stretcher airlifted from US ship after collision

The collision tore a gash below the Fitzgerald's waterline, sending water gushing into several compartments and killing seven sailors in what was the greatest loss of life on a US Navy vessel since the USS Cole was bombed in Yemen's Aden harbour in 2000.

Those who died were in their berthing compartments, while the Fitzgerald's commander was injured in his cabin, suggesting no alarm warning of an imminent collision was sounded.

A spokesman for the US Navy's 7th Fleet in Yokosuka, the Fitzgerald's home port, said he was unable to comment on an ongoing investigation.

The incident has spurred six investigations, including two internal hearings by the US Navy and a probe by the United States Coast Guard (USCG) on behalf of the National Transportation Safety Board.

The Japan Transport Safety Board, the Japanese Coast Guard (JCG) and the Philippines Government are also conducting separate investigations.

Spokesmen from the JCG, US Coast Guard and ship owner Dainichi Invest also declined to comment.

'Confusion', container ship continued

Sorry, this video has expired Damaged USS Fitzgerald returns to port after collision at sea

The investigations will examine witness testimony and electronic data to determine how a naval destroyer fitted with sophisticated radar could be struck by a vessel more than three times its size.

Another focus of the probes has been the length of time it took the ACX Crystal to report the collision.

The JCG said it was first notified at 2:25am (local time) — nearly an hour after the accident.

In his report, the ACX Crystal's captain said there was "confusion" on his ship's bridge, and that it turned around and returned to the collision site after continuing for 11 kilometres.

Shipping data shows the ACX Crystal, chartered by Japan's Nippon Yusen KK, made a complete U-turn between 12:58am and 2:46am (local time).

Reuters