SEOUL/OSLO (Reuters) - A fire that spread across two oil tankers in a South Korean port injured 10 people on Saturday, coastguard and fire officials said, adding the blaze had largely been put out.

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An explosion occurred on the Stolt Groenland, a 25,000-tonne, Cayman Island-flagged oil tanker, at the southern port of Ulsan at around 10:50 a.m. (0150 GMT), a coastguard official said.

There were 25 sailors aboard, including Russians and Filipinos.

The fire spread to another oil tanker docked nearby, the 9,000-tonne, South Korean-flagged Bow Dalian, with 21 aboard, he said.

All of the sailors on both ships were rescued, but 10 people, most of whom were workers at the terminal, have been wounded so far, a fire official told Reuters. Nine of them were South Korean, including one in a critical condition, and the other was from India.

“The fire has largely been put out but we are checking inside the vessels if there are any flames left or smoke coming out,” the first official said.

Any impact on the terminal’s output or the surrounding environment appears minimal for now as the ships were at the port for repair, he added.

The Coast Guard is investigating the cause of the incident, officials said.

Stolt Tankers, a unit of Oslo-listed Stolt-Nielsen which owns the first ship, expressed concern about the incident.

“The safety of all people on site and the protection of the environment is paramount to the company’s operations,” it said in a statement.

Norway’s Odfjell, which owns the other vessel, Bow Dalian, said the ship had been towed to safety and its crew accounted for.

“One of our crew members is undergoing treatment for light injuries stemming from the fire,” Odfjell spokeswoman Anngun Dybsland said.