Updated at 12:44 p.m. ET
(AP) MOBILE, Ala. - Authorities sent divers and sonar-equipped boats Wednesday to the sunken wreckage of a U.S. Coast Guard helicopter that crashed in Alabama's Mobile Bay on a training mission, leaving one crewmember dead and three others missing.
The MH-65C helicopter crashed Tuesday evening near Point Clear, Ala. One crewmember was found unresponsive and later declared dead, the Coast Guard said.
The man who died was a rescue swimmer, said Capt. Don Rose, commanding officer of Coast Guard Sector Mobile. The three missing crewmembers were the pilot, the co-pilot and the flight mechanic.
Rose said rescuers tried to revive the rescue swimmer when they found him, but were unable to.
Names of the four crewmembers have not been released.
The crewmembers were outfitted with survival gear for the water, which was just over 60 degrees Fahrenheit overnight.
"These guys are wearing survival equipment, they're wearing what we call dry suits to protect them from the cold water," Rose said.
Chief Petty Officer John Edwards said divers overnight had gone to the site of the helicopter, in about 13 feet of water, but were unable to gain access to its fuselage. He said they planned to try again Wednesday with hopes of confirming whether the crewmembers were inside.
"The sun is up, which improves things greatly," Edwards said.
Timothy Shiver, a volunteer with North Baldwin County Search and Rescue, said he and about 15 members of his group were among those helping with the search overnight. He said the water was rough and that dozens of boats were involved in the search.
At midmorning, under overcast skies and sprinkles of rain, eight rescue workers from the North Baldwin group set out again in two boats equipped with sonar. Their spokesman, James Phillips, said they were working under directions from the Coast Guard, and were tasked with using the sonar to find debris. He said they also brought a diver, but the diver had not yet been instructed to enter the choppy water.
The accident comes less than three years after an HH60 Jayhawk helicopter crashed off James Island in Washington state in July 2010, killing three Coast Guard crew members.
Tuesday's wreck also brought back memories in south Alabama of a 1981 crash of a Coast Guard helicopter near an airport in Mobile that killed all four people aboard.
The MH-65C, commonly referred to as the Dolphin, is a twin-engine, single-rotor helicopter often used in search and rescue operations. A Coast Guard website said the typical crew includes two pilots, a flight mechanic and a rescue swimmer.
The Coast Guard had major problems with engine failures in the French-designed aircraft and began replacing the helicopter's power plants in 2004, according to a report from the General Accounting Office. Pilots reported 67 cases of engine failures or other problems over a six-month period ending in February 2004, the report said.
The Coast Guard began an engine replacement program costing as much as $250 million to solve the problem, according to the report. Originally known as the HH-65, Dolphin helicopters with new engines, communication equipment and weapons were designated as the MH-65C, the type of helicopter that went down in Mobile Bay.
Edwards said the helicopter that crashed received the improved engine several years ago, but it wasn't immediately clear exactly when.
"They're new engines as far as engines go, but they're not brand-spanking new," he said. The improvements seem to have fixed the engine problems from years ago since no new rash of failures or crashes has occurred, he said.
The last deaths in an HH-65 were in September 2008, when four crew members died when a helicopter went down off the coast of Hawaii, according to a Coast Guard database. A rescue cable snapped during a training mission and metal flew into the rotor blades, an investigation found.
The aircraft that crashed Tuesday had departed the Aviation Training Center in Mobile on a training mission, Petty Officer 2nd Class Elizabeth Bordelon said.
Coast Guard officials say it went down about two to three miles southwest of Point Clear. The three missing are all Coast Guard members.
"Our thoughts and prayers are with the families of the crewmembers during this difficult time," Capt. Don Rose, commanding officer of Coast Guard Sector Mobile, said in a statement.
The Coast Guard said two helicopters, an airplane and several vessels were involved in the search.
National Weather Service officials said winds in the area Tuesday night were southeast at about 15 mph.