ANCHORAGE, Alaska (AP) – Two British sailors were killed in an explosion aboard a Royal Navy nuclear-powered submarine in the Arctic Ocean. An injured crewmember was evacuated to a hospital in Anchorage, officials said Wednesday.

The explosion occurred late Tuesday aboard the HMS Tireless, which was submerged under an ice cap about 170 miles north of Deadhorse. The submarine was conducting a joint exercise with the United States when its air purification system malfunctioned, British defense officials said.

According to the U.S. Navy, a self-contained oxygen generation candle exploded. The attack submarine surfaced quickly and its nuclear reactor was not affected, according to the British Ministry of Defense. The Tireless does not carry nuclear missiles.

The injured sailor, whose name was not released, was transported by the Alaska Air National Guard from Deadhorse, in northern Alaska’s Prudhoe Bay, to Kulis Air National Guard Base in Anchorage, 625 miles away, where an ambulance took him to a local hospital.

He was taken to Alaska Regional Hospital where he was in stable condition, said hospital spokeswoman Kjerstin Lastufka.

The Tireless was operating with the USS Alexandria in a joint operation to test submarine operability and tactical development in Arctic waters. The submarine’s forward compartment was damaged in the explosion. The submarine was forced to surface quickly through the ice.

The equipment that failed had a 100 percent safety record, according to a Ministry of Defense spokesman. The piece of air-purification equipment was fitted to the submarine as part of an update in 2001.

“I am deeply saddened at the loss of the crew members from the Tireless,” said U.S. Navy Vice Adm. Jay Donnelly, commander of the Submarine Force. “We stand by to assist in any way we can.”

The Alaska Air National Guard in Anchorage received a call at 10:30 p.m. Tuesday alerting the Rescue Coordination Center of the explosion aboard the British submarine.

An HC-130 refueling tanker was launched from Kulis 57 minutes later, reaching Deadhorse at 1:26 a.m., said Kalei Brooks, spokeswoman for the Alaska Air National Guard. The HC-130 had about six people aboard, including two pararescuemen, a pilot, co-pilot and crew chief.

A private helicopter brought the injured sailor to Deadhorse. The sailor was then taken back to Kulis aboard the HC-130 where an ambulance was waiting.

“He was initially reported to have some burns,” Brooks said.

Since 1986, every Arctic tactical exercise has involved both U.S. Navy and Royal Navy submarines.

Lt. Col. Andy Price, spokesman for the Royal Navy, said the submarine, while fully functional, will be evaluated over the next 12 hours to determine whether it will continue to be part of the joint exercises or return to the United Kingdom. Two weeks of exercises are scheduled to end March 30.