A United States military plane carrying five American personnel hit a concrete barrier while attempting to take off from a road during a contingency training in a northern Philippine province, injuring all those aboard, Philippine officials said Wednesday.

The pilot and two other American personnel were brought to a hospital for treatment after Tuesday afternoon’s accident in a concrete bypass road in Laoac town in Pangasinan province. Two other injured personnel were treated at the site, police said in an initial report.

The training that involved a US Air Force transport aircraft landing on and taking off from an “alternate landing zone” was planned and fully coordinated with Philippine civilian, police, and military authorities, three Philippine officials told The Associated Press, adding that the cause of the accident was under investigation. The three officials spoke to The AP on condition of anonymity because they were not authorized to discuss the accident publicly.

The aircraft managed to land during the “supervised activity,” but swerved during takeoff, one of the three officials said, adding that such unique training was needed to brace military forces for all types of contingencies, including when regular airports and runways become inaccessible during typhoons and earthquakes.

US forces are allowed to conduct training with Filipino counterparts in the Philippines under a 1999 Visiting Forces Agreement. Large-scale joint combat training drills in recent years have focused on helping the Philippines defend its territorial interests and promote freedom of navigation and overflight in the South China Sea, which lies west of Pangasinan.

Confrontations between the coast guard and naval forces of China and the Philippines have flared in recent years in the disputed waters, which is claimed largely by Beijing. Vietnam, Malaysia, Brunei, and Taiwan are also involved in the long-simmering territorial standoffs.

The US does not lay any claims in the contested waters but has repeatedly warned that it’s obligated to defend the Philippines under a Mutual Defense Treaty if Philippine forces, ships, and aircraft come under an armed attack, including in the South China Sea.