A US Navy helicopter crashed into the sea off the coast of San Diago on Tuesday after it took off from the USS Abraham Lincoln, the US Pacific Fleet said.
The US MH-60S helicopter crashed around 60 nautical miles (around 111 kilometers) off the San Diego coast at 4.30 p.m. local time (2330GMT) while conducting routine flight operations, the fleet said on Twitter.
One crewmember was rescued while search efforts continue for the other people, it added.
No information was shared on how many people were on board the helicopter.
"Search and rescue operations are ongoing with multiple Coast Guard and Navy air and surface assets," the statement said, adding that Abraham Lincoln has been homeported in San Diego.