Authorities say there were five personnel aboard the MH-53E helicopter when it went down in the Atlantic Ocean at about 11 a.m. ET. According to ABC News, four people were rescued from chilly, 42-degree waters and were rushed to Sentara Norfolk General Hospital.
Two of the rescued crewmembers later died. Two are in stable condition.
Navy spokesman Cmdr. Mike Kafka said the helicopter made an emergency water landing about 20 miles east of the Fort Story/Virginia Beach area." The helicopter was conducting a routine training mission with another helicopter.
When the helicopter went down, the other helicopter was able to rescue the four crew members. The search continues for the fifth person, who remains unaccounted for.
The cause of the crash is unknown at this time.
The MH-53E is a variant of the CH-53 heavy lift helicopter that is used as a minesweeper. The CH-53's are the largest helicopters in the U.S. military's inventory.
ABC News contributed to this report.