SAN DIEGO -- President Trump said in a tweet Wednesday morning four U.S. Marines from the 3rd Marine Aircraft Wing were killed in a helicopter crash Tuesday in Southern California. He said "our thoughts and prayers" are with the Marines.
"We pray for their families, and our great @USMC," he tweeted.
The Marine helicopter crashed during a training mission. The military previously said that all four crew members were believed killed.
The CH-53E Super Stallion went down shortly after 2:30 p.m. Tuesday near El Centro, a few miles from the U.S.-Mexico border. El Centro is approximately 113 miles east of San Diego, CBS San Diego affiliate KFMB-TV notes.
The helicopter was with the 3rd Marine Aircraft Wing out of the Miramar air station in San Diego, according to a base press statement. The cause of the crash is under investigation.
The nearby Naval Air Facility El Centro messaged that the crash site was north of Plaster City, west of El Centro.
The names of the crew members will be withheld until 24 hours after their relatives are notified, the Miramar base said.
The incident is the deadliest Marine aircraft crash since a KC130T transport plane went down in Mississippi last July, killing 15 Marines and a sailor. Last October, a CH-53E helicopter crashed and burned in Okinawa but nobody was injured.
The CH-53E Super Stallion is the largest helicopter in the U.S. military. It is used for minesweeping and transport and can carry dozens of troops and tons of cargo. In 2005, 31 people died when a CH-53E helicopter went down in Iraq during a sandstorm.