A crane-carrying vessel collided with an oil tanker off of South Korea's west coast on Friday, causing more than 66,000 barrels of crude oil to spill in what was believed to be South Korea's largest offshore oil leak, officials said.

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Officials at the Maritime and Fisheries Ministry, citing Coast Guard reports, initially said about 110,000 barrels had leaked from the Hong Kong-registered tanker. But the Coast Guard later said additional information indicated the amount was significantly lower — about 66,043 barrels.

The accident occurred around 7:30 a.m. when the crane-carrying vessel slammed into the 146,000-ton tanker Hebei Spirit in waters 5 miles off Mallipo beach, some 93 miles southwest of Seoul.

The extent of the spill's potential damage to communities or wildlife in the area was not immediately clear, a ministry official said on customary condition of anonymity citing office policy.

Jung Se-hi, a Coast Guard officer, said it dispatched 34 coast guard, navy and other government vessels as well as four helicopters to stop the spread of the spill and collect the oil.

He said an emergency floating fence was also set up around the scene but added it would take at least several days to complete the operation.

The Coast Guard said in a statement that the collision left holes in three containers aboard the tanker. Spills from two containers were later stopped, but oil was still leaking from the third container.

YTN, a 24-hour cable news channel, showed footage of the black oil gushing out of the ship and into the ocean.

The tanker was carrying about 260,000 tons of crude oil — or about 1.8 million barrels, another ministry official said, also speaking on condition of anonymity in line with policy.

Officials at the ministry and the Coast Guard said the accident was believed to be South Korea's largest offshore oil leak.

The previously largest oil spill in South Korea happened in 1995 when about 5,035 tons — some 35,000 barrels — of crude and fuel oil was leaked, according to South Korea's Yonhap news agency.

In 1989, the Exxon Valdez supertanker released about 260,000 barrels, or 11 million gallons of oil into Alaska's Prince William Sound in what turned into a major environmental disaster.