A Japanese tanker spilled about 1.4 million gallons of crude oil in the eastern Indian Ocean following a collision with a cargo ship, the tanker's operator said Tuesday.

Japan's Kyodo news service said the spill — which would be about 4,500 tons — may have been the largest ever involving a Japanese tanker.

The Bright Artemis tanker spilled the oil following a collision Monday with the Amar, a smaller cargo ship, Mitsui O.S.K. Lines said in a statement. It said the accident took place when the tanker maneuvered near the Amar, which was in distress about 300 miles west of India's Nicobar islands.

The exact amount of the spill was not clear, the announcement said. The tanker was carrying about 77.6 million gallons, or 250,000 tons, of crude. It had left port in Oman bound for Japan.

There were no reports of injuries aboard the tanker, which had a Croatian captain and crew of 23, or the Amar, which was registered in Singapore.

Mitsui said the spill had been reported to Singaporean and Indian Coast Guard officials.

The largest oil spill involving a U.S. vessel occurred when the Exxon Valdez oil tanker emptied 11 million gallons of crude oil into Prince William Sound off the coast of Alaska in 1989, killing hundreds of thousands of birds and marine animals and soiling more than 1,200 miles of rocky beach