Updated at 5:05 a.m. ET: MOBILE, Alabama -- One crew-member died and three were missing after a U.S. Coast Guard helicopter crashed off Alabama's coast on Tuesday.

The Coast Guard said in a statement early Wednesday that one crew-member was found unresponsive and was later declared dead.

Petty Officer Second Class Elizabeth Bordelon said the MH-65 Dolphin crashed just after 8:30 p.m. local time (9:30 p.m. ET) in Mobile Bay near Point Clear, Alabama.

The flight originated from the Aviation Training Center in Mobile, Bordelon said.

A response cutter from Dauphin Island and two additional MH-65s from New Orleans were dispatched to assist in the search, she said.

A Mobile County Sheriff's Flotilla crew, an HU-144 twin-engine aircraft and an Alabama Marine Resources vessel were also activated.

"Our thoughts and prayers are with the families of the crew-members during this difficult time," the Coast Guard said in a statement, adding that it was working through the night to find the three missing crew-members.

"This is our family we're talking about," Bordelon told the Mobile Press-Register.

The Press-Register reported that winds were southeast at around 15 miles per hour and the water temperature 63 degrees Fahrenheit on Tuesday night. Average water depth in the area averages at 13 feet, the newspaper said.

According to an overview on the U.S. Coast Guard website, the MH-65 Dolphin is its "most ubiquitous aircraft."

It is "certified for operation in all-weather and night-time operations, with the exception of icing conditions," the overview says.

The cause of the crash was not immediately known.

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Msnbc.com staff, The Associated Press and Reuters contributed to this report.