Navy research sub catches fire off California

All 43 crew members rescued

A file photo of the USS Dolphin

(CNN) -- Military teams responded Wednesday to a fire on a Navy research submarine off the coast of California.

The blaze aboard the USS Dolphin broke out Tuesday night. All 43 crew members on board the submarine were rescued -- 41 by a Navy ship, and two by helicopter from the water, Pentagon officials said Wednesday.

Officials said it was unclear whether the fire was still burning as a towing vessel and other equipment arrived at the scene, about 100 miles from San Diego, California.

The fire broke out around 11:30 p.m. Tuesday. The submarine was on the surface when the fire started, and it partially flooded as water entered through the open hatches.

The Dolphin is one of the Navy's only operational diesel-electric, deep-diving, research and development submarines. It carries scientific and technical payloads of up to 12 tons, and has extensive onboard laboratories.

According to the Navy, the Dolphin holds the world-depth record of 3,000 feet for operational submarines.

The Dolphin has been outfitted to test advanced Navy sonar equipment and conducts civilian research.

The fire on the Dolphin comes 34 years to the day after the nuclear-powered submarine USS Scorpion was lost at sea in an accident that took the lives of all 97 crew members. The sub was only five days short of its return to port at Norfolk, Virginia.

Many details of that disaster remain classified, and the Navy has said it does not know the cause of the sinking. The wreckage was found in the Atlantic at a depth of 10,000 feet, about 400 miles southwest of the Azores.

Reports have cited a mid-1980s study that showed no radiation leaking from the Scorpion's nuclear reactor or its two nuclear-tipped torpedoes.

CNN Producer Paul Courson contributed to this report.