Supertanker blast scare blamed on "freak wave"

The M Star oil tanker is seen in the sea near Japan in this December 2008 handout photograph released on July 28, 2010 by the ship's owners Mitsui O.S.K. Lines Ltd.

FUJAIRAH, United Arab Emirates (Reuters) - A Japanese supertanker, which stirred fears of an attack in the Strait of Hormuz, diverted to a UAE port on Wednesday where officials said the damage was caused by a freak wave.

Forty percent of the world's seaborne oil passes through the narrow Strait, gateway to the oil-producing Gulf, where Al Qaeda has threatened to attack shipping.

Japan's transport ministry said there was an "explosion" at around 00:30 a.m. local time and cited the possibility of an attack on the ship, but port officials said there was no evidence.

No oil leaked from the supertanker, named M Star, although some members of the 31-strong crew were injured, said a general manager at the UAE port of Fujairah.

"The cause of the incident was a freak wave and there is damage in the upper accommodation decks of the ship," he said.

The ship moored near the port for repairs.

Oman's coastguard cited "a tremor" as the cause of the incident, while an official from the Omani transport ministry said it was "business as usual" in the Strait.

A seismologist in Iran, which with the United Arab Emirates and Oman borders the Strait, said there had been an earthquake in the region, although the U.S. Geological Survey said it had no record of a tremor.

Captains of other ships near the incident also mentioned an earthquake, Attollah Sadr, head of Iran's Ports and Maritime Organization, was quoted as saying by Mehr news agency.

CAUSE INVESTIGATED

UAE port officials said they were investigating the cause of the incident, which shipowner Mitsui O.S.K. earlier said could have been an attack.

"A crew member saw light on the horizon just before the explosion, so (Mitsui O.S.K.) believes there is a possibility it was caused by an outside attack," Japan's ministry said in a statement.

The U.S. Navy's Fifth Fleet based in Bahrain issued a statement saying the cause of the incident was unknown.

"Initial damage assessment from the ship's owner, Mitsui O.S.K. Lines Ltd, Japan, is that one life boat was blown off the ship and there is some damage to the starboard hatches," it said.

On board were 16 Filipino and 15 Indian crew members.

The tanker, bound for Chiba, near Tokyo, is carrying around 2.3 million barrels of Qatar Land and Abu Dhabi Lower Zakum crudes, industry sources said.

Any impact on the Asian spot crude market would be negligible and the tanker would have taken three weeks to arrive in Japan, traders said.

"This (event) won't stop the flow of crude, so there will be no impact on what is able to be bought," a Tokyo-based crude trader said.

Around 17 million barrels per day of oil flow via the Strait of Hormuz, and Middle East crude accounts for 90 percent of Japan's total imports.

(Reporting by Yoko Nishikawa, Osamu Tsukimori and James Topham in Tokyo; Alejandro Barbojosa, Luke Pachymuthu in Singapore; Saleh al-Shaibany in Muscat; Raissa Kasolowsky, Amran Abocar and Amena Bakr in Dubai; Frederik Richter in Bahrain; Writing by Barbara Lewis; Editing by Jason Neely)