SEOUL, South Korea — U.S. specialists began aiding a massive sea and land battle Friday to try to contain and clean up 2.7 million gallons of crude oil from South Korea's worst oil spill.

The team of U.S. Coast Guard experts arrived Thursday to aid the hundreds of vessels involved in containing the spill. An expert from the U.S. National Oceanic and Atmospheric Administration also is assisting.

A barge carrying a crane lost control and slammed into the supertanker Hebei Spirit off the west coast Dec. 7, spilling oil that polluted hundreds of seafood farms and turned scenic beaches black.

The National Emergency Management Agency said the spill has contaminated 104 miles of coast in Taean County, about 95 miles southwest of Seoul.

The agency said 339 seafood farms have been hit and an additional 220 farms were expected to be affected.

About 220 ships, including Coast Guard, navy and private fishing boats, and 14 helicopters have been involved in the effort to try to contain the slick, the Coast Guard said. More than 21,000 troops, public officials, residents and volunteers worked on shore, it said.

"We're continuing the operation at night, mobilizing ships equipped with searchlights," said Lee Won-yol, a Coast Guard official in Taean. "But the weather is not good. Winds are strong and waves are high."