Two British Submariners Killed Under Ice

Two submariners on HMS Tireless (S-88) were killed by an "explosion" of an O₂ candle while the sub was operating under the Arctic ice during ICEX-2007. From the U.S. Navy press release:

The Royal Navy submarine HMS Tireless, participating in the Joint U.S. Navy/Royal Navy Ice Exercise 2007 (ICEX-2007) in the Arctic Ocean, experienced an explosion of a self contained oxygen generation candle that killed two crew members and injured one.
The explosion occurred at approximately 12:20 a.m. (EDT) March 21.
The injured member of the crew has been transported by an Alaska Air National Guard C-130 to Anchorage for treatment.
“I am deeply saddened at the loss of the crewmembers from the Tireless,” said Vice Adm. Jay Donnelly, Commander, Submarine Force. “Submariners are brothers at sea and we all feel the loss as if it were our own. We stand by to continue to assist in any way we can.”
ICEX-2007 and Royal Navy officials have confirmed that the Tireless is safe and operational and that a full assessment is being conducted.

This article from The Scotsman has more on oxygen (also known as "chlorate") candles as they're used on British subs:

Chlorate candles have been used to create oxygen on submarines since the Second World War, usually as an emergency measure if the vessel's rises to dangerous levels. According to the navy source, one such candle was ignited yesterday on board HMS Tireless, as a part of training...
...An MoD spokesman said the chlorate candles on board HMS Tireless had never failed before and, until then, had a 100 per cent safety record. Even so, their use on other boats had been restricted until safety checks could be carried out, he said.
A former sailor on British nuclear submarines insisted chlorate candles are known by crew to be dangerous. The mariner, who asked not to be named, said: "It's not a candle like you'd think - there's no open flame. It's ignited in a metal canister with a .22 bullet and they burn without any flame.
"Everyone on board will have been trained how to use them. They have definitely been known to explode before - high heat and oxygen is a combustible mix - but I couldn't imagine the force would have killed two men. Something else must have gone wrong.
"The candles line the entire sub and are used in an emergency. Next to each is a pair of asbestos gloves and a bucket of water. If you see the candle is starting to flame or burn, you simply put on the gloves and dump it into the water.

An explosion and/or fire onboard a submarine while it's under ice was always one of those "worst case" disaster scenarios you talked through during advanced damage control training. Luckily, the ice in this case was thin enough to break through, and the crew of the Tireless was able to skillfully make it to the surface.

Staying at PD...

Update 2029 21 March: Midwatch Cowboy has more on the story.

Update 2035 22 March: The lost submariners have been identified as Operator Maintainer Anthony Huntrod, 20, and Leading Operator Mechanic Paul McCann, 32. Sailors, rest your oars.