A technical malfunction has been blamed for two separate fires on an International Seaways tanker in Alaska.

The exhaust stack on the 50,000-dwt Atlantic Lily (built 2008) suffered blazes on Friday evening and Saturday morning at the Port of Alaska in Anchorage.

The Anchorage Daily News reported officials as saying both fires were quickly contained by crew members, who were not injured.

There was no damage to the port, but damage to the Hong Kong-flag MR is unclear.

International Seaways confirmed the vessel experienced an exhaust stack fire over the weekend, which was quickly brought under control.

“Thanks to a swift, professional response by the crew and local authorities, the fire was quickly extinguished with no injuries or damage to the vessel and no pollution,” the company said.

The vessel was able to complete cargo operations and resume its voyage on Sunday.

Anchorage Fire Department responded on Friday evening after a report of “a very, very large backfire boom that everybody heard” at the port, the department’s assistant chief, Alex Boyd, said on Saturday.

This was caused by the ignition of fuel vapour in the stack, he added.

Visible flames shot from the vessel, but by the time firefighters arrived, the blaze had been extinguished.

The US Coast Guard said: “At approximately 10pm, thick, black smoke was seen billowing from the exhaust stack of the 600-foot foreign-flagged tank vessel, following by a loud boom and flames.”

Jet fuel cargo

The ship was unloading 300,000 barrels of jet fuel for use at Ted Stevens Anchorage International Airport, according to the city authority.

“The boiler will not be restarted until after fuel offloading is complete, probably early Sunday,” it said. “Atlantic Lily officials hope to complete repairs and testing and to get US Coast Guard approval to depart late Sunday morning or early afternoon.”

Coast Guard officials boarded the tanker to monitor the situation.

Unloading had resumed and repairs were being made.

The Coast Guard added: “It was determined that an issue with the vessel’s auxiliary boiler caused an improper fuel-to-air mixture, igniting a build-up of soot in the exhaust stack, which resulted in a loud boom and flames.”

On Saturday morning, the unburned fuel within the stack again ignited, causing a similar small fire.

The crew again dealt with this.

The Atlantic Lily has insurance cover through the UK P&I Club.