Two Malaysian military helicopters collided and crashed during a training session on Tuesday, killing all 10 people on board, the navy said.

The helicopters were rehearsing at a naval base in northern Perak state for the navy’s 90th anniversary celebration next month when the accident occurred, the navy said in a brief statement.

“All victims were confirmed dead on site,” it said, adding that the remains have been sent to the hospital to be identified.

A video circulating on social media purported to be of the incident showed several helicopters flying low in a formation. One of the helicopters veered sideways and clipped the rotor of another helicopter, causing both to plunge and crash.

Seven crew members were aboard the AW139 maritime operation helicopter, the navy said. That aircraft is produced by AgustaWestland, which is a subsidiary of the Italian defense contractor Leonardo. Three other crew members were on a Fennec lightweight helicopter, manufactured by European multinational defense conglomerate Airbus.

Local media reported that the AW139 crashed at a sports complex at the naval base, while the Fennec hit a nearby swimming pool.

The navy said it will launch an investigation to determine what caused the accident.