A supertanker ran aground July 2 in Tokyo Bay, dumping as much as 15,000 kiloliters of crude oil in one of the worst environmental accidents in Japanese waters, the Maritime Safety Agency said.

The 147,012-ton Diamond Grace, a Panamanian-registered vessel, was reportedly carrying about 257,000 tons of crude oil when it ran aground at 10:05 a.m. about 6 km southeast of Yokohama's Honmoku pier. "This is the worst oil spill Japan has ever experienced," Transport Minister Makoto Koga said. The oil stopped leaking by 1 p.m. The cause of the accident is under investigation.

As of 7 p.m., the slick measured about 7 km east to west and some 9.5 km north to south off Higashi Ogishima in Kawasaki. It was drifting northeast toward the Tokyo and Chiba waterfront areas. Because the spill has dispersed, the chance of it erupting into flames is now slim, according to the MSA. "July 3 and July 4 will be extremely important" in the cleanup process, Koga said. "We are putting all the effort we have into the operation."

Dressed in working clothes, Koga appeared at a news conference after returning from an inspection of the accident site. Koga said priority is being given to preventing the slick from spreading further and preventing oil left in the tanker from leaking. The minister added that officials would repair holes in the tanker this morning and will later start extracting oil from the ruptured tanks, an operation that is hoped to be finished by 2 p.m. July 5.

Shortly after noon, Prime Minister Ryutaro Hashimoto set up an emergency task force to handle the the spill, Teijiro Furukawa, deputy chief Cabinet secretary, said. The task force instructed the MSA and the Maritime Self-Defense Force to set up containment booms and to collect the oil, Furukawa said. Hashimoto met with representatives of various agencies to discuss the accident and ways to minimize the damage before deciding to set up the task force.

The spill is expected to reach the center of Tokyo Bay early July 4, leaving the leading edge of the slick 2.2 km from shore, according to a simulation by the Petroleum Association of Japan. It said the slick is expected to move about 14 km northeast from its original location within 24 hours.

The spill could be as close as 2.5 km to Kawasaki's Ogishima Pier this morning, while it is likely to be 2.2 km off Sodegaura, Chiba Prefecture, early July 4, it said. The 3,526-ton Seiryumaru, Japan's best oil cleanup vessel, left Nagoya for Tokyo Bay on July 2. The ship is scheduled to arrive at the site of the spill at about noon July 3 to join other vessels in cleanup operations. MSA officials expressed pessimism over the cleanup operation.

"July 3 and July 4 will be the most important. It is difficult to encircle all the spilled oil (with an oil barrier)," said an agency official. The official did not rule out the possibility that the oil slick will wash ashore. As time goes by, the oil will thicken and grow in volume as it absorbs water, making it more difficult to handle and collect, the official said.