VIRGINIA BEACH, Va. >>  A Navy helicopter with five crew members went down in the Atlantic off the Virginia coast during a routine mission today, killing two crew members and injuring two, the U.S. Navy said. Rescuers were still looking for a fifth person.

Two of the crew members who were hoisted with two others from the chilly, 42-degree waters by a Navyhelicopter later died, the Navy said. The other two were taken to Sentara Norfolk General Hospital.

“Today has definitely been a tough day on all of us,” Capt. Todd Flannery, the commander of HelicopterSea Combat Wing Atlantic, said at a news conference. “Our heartfelt prayers go out to the families and loved ones of those killed and injured in today’s crash.”

The Navy identified the aircraft as an MH-53E. The helicopter, assigned to Helicopter Mine Countermeasures Squadron Fourteen based at Naval Station Norfolk, was conducting routine training operations at the time of the crash, the Navy said.

According to the Naval Air Systems Command website, the aircraft performs airborne mine countermeasures and onboard delivery missions. It holds a crew of up to eight, including two pilots and is capable of speeds of more than 170 mph.

The three-engine helicopter measures 99 feet long and more than 28 feet tall. It has a maximum gross weight of 69,750 pounds.

It was not immediately known why the chopper went down about 20 miles from Virginia Beach, and the Navy said the crash is under investigation.

Coast Guard Petty Officer David Weydert said two Coast Guard vessels, including a cutter, responded to the scene.

The Navy said the identity of the dead crewman would be released 24 hours after his family was notified.

The Navy said crewmembers were wearing survival suits designed to keep water away from the body.

However, an adult could survive one to three hours in 40 to 50 degree water and would become exhausted or unconscious between 30 and 60 minutes, according to the Personal Flotation Device Manufacturers Association website. Survival also varies based on body size, body fat percentage and movement in the water.

In July 2012, two crew members were killed when the same model helicopter crashed into a canyon in the Gulf nation of Oman while lifting a downed aircraft.

According to a Navy investigation obtained by The Virginian-Pilot in November, the crash of the $50 million helicopter revealed a series of problems within the Navy Sea Dragon program, which is headquartered in Norfolk. In that specific incident, the report blamed the crew for skipping preflight safety checks and for failing to develop a concrete plan for how and when to abort the mission.

But Flannery told the newspaper following the investigation that the Navy has invested millions of dollars to upgrade and better maintain its remaining 29 Sea Dragon airframes since the crash, including adding more than 100 maintenance personnel to the Norfolk-based squadrons.

The Navy had planned to phase them out beginning in the mid-2000s, but kept the Sea Dragons flying because the service had no viable replacement.

At the news conference, Flannery said he doesn’t have any concerns about the safety of the aircraft.