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."