CANBERRA, Australia (AP) — The three U.S. Marines killed in a tiltrotor aircraft crash during a training exercise in Australia were from Illinois, Virginia and Colorado and another Marine was in critical condition, the Marine Corps said Tuesday.

The Marine V-22B Osprey with 23 Marines on board crashed Sunday in tropical forest on Melville Island while taking part in Exercise Predators Run, a drill that includes the militaries of Australia, Indonesia, the Philippines and East Timor.

All 20 survivors were injured and were flown by rescue aircraft 80 kilometers (50 miles) south to the city of Darwin within hours of the crash. Three of those Marines remained in Royal Darwin Hospital on Tuesday, one in critical condition and two stable, a Marines statement said. Their names have not been released.

Up to 2,500 U.S. Marines have been based in Darwin for six months a year since 2012 as part of the U.S. military pivot to Asia to counter China’s growing influence in the region.

Col. Brendan Sullivan, the commanding officer of the Marine Rotation Force-Darwin, said the Marines’ focus was on supporting the recovery of wreckage and investigating the cause.

“We are deeply saddened by the loss of three respected and beloved members of the MRF-D family,” Sullivan said in a statement.

“Our thoughts and prayers remain with the families and with all involved,” Sullivan added.

The three killed were Osprey pilot Capt. Eleanor V. Beau, 29, originally of Belleville, Illinois; Cpl. Spencer R. Collart, 21, from Arlington, Virginia, and Maj. Tobin J. Lewis, 37, from Jefferson, Colorado. All were based in Darwin.

President Joe Biden has also offered his condolences to their families.

“Jill and I send our deepest condolences to the families of the Marines who lost their lives in this deadly crash,” Biden tweeted, referring to his wife Jill Biden. “We are praying for those who also suffered injuries.”

The Osprey is a hybrid aircraft that takes off and lands like a helicopter but during flight can tilt its propellers forward and cruise much faster like an airplane.

Before Sunday, there had been five fatal crashes of Marine Ospreys since 2012, causing a total of 16 deaths.

Three Marines were killed when an Osprey plunged into the Coral Sea off Australia’s northeast coast in 2017. The remaining 23 people on board were rescued.