Maritime authorities confirmed Monday that over 200 times more oil than initially expected leaked into waters off the south coast of Korea in an oil tanker collision, drawing concerns over the potential damage.

According to the Yeosu Coast Guard, about 164 tons of oil spewed into the sea after Singapore-registered oil tanker Wu Yi San collided with a bridge while approaching a pier in Yeosu, South Jeolla Province, on Friday. This amounts to 164,000 liters of oil.

Three pipelines connecting to petrochemical companies in the Yeosu industrial complex were damaged, causing oil in the pipelines to spill into the water, officials said.

A crew of 25 was on board the tanker, mostly Chinese, and no causalities werereported.

The maritime police also confirmed that a coast pilot’s negligence caused the accident.

“The coast pilot was operating the tanker at 7 knots, violating speed safety,” said Kim Sang-bae, the chief of the Yeosu Coast Guard.

Oil tankers are required to lower their speed to 2-3 knots near the port and shut down engines when approaching the pier. Four supporting ships then slowly push the tanker to the final destination.

All entries and departures of large vessels at Yeosu port should be operated by city coast pilots according to regulations. Two Yeosu coast pilots boarded the tanker 90 minutes before the accident.

The concerned coast pilot reportedly has more than 20 years of work experience.

The maritime police denied reports that the pilot was navigating the tanker while drunk.

Officials dispatched 111 vessels and 5 helicopters and deployed hundreds of workers to contain the oil spill. They also built a 10-kilometer oil fence along the shore.

Around 70 percent of the oil has been collected, the police said. At least 10 days will be taken to complete the clean-up, they added.

Shallow films of oil were found in some areas 10 kilometers from the pier, escalating concerns over it spreading further. A total of 51 fish farms are situated within the 10-kilometer radius.

The maritime authorities will summon the concerned officials and continue a thorough investigation, they said.

By Lee Hyun-jeong (rene@heraldcorp.com)