MANILA, Philippines (AP) – A newly delivered Philippine assault helicopter crashed during a night training exercise north of Manila, killing all six air force members on board, have officials announced Thursday.

Defense Secretary Delfin Lorenzana said it is still unclear why the S-70i Blackhawk helicopter carrying three pilots and three crew members crashed on Wednesday evening near Clark Air Base, a former military base. American which is now a bustling industrial and leisure complex.

“No survivors have been found,” Air Force spokesman Lt. Col. Maynard Mariano said, adding that similar Blackhawks had been grounded as part of an investigation into the the accident. “We mourn the loss. “

The helicopter took off from Clark in Pampanga province for the two-hour training exercise but did not return as planned. A search and rescue team then found the wreckage, Mariano said without giving further details.

The Department of Defense finalized a deal to acquire 16 Blackhawks for $ 241 million in 2019 as part of a military program to modernize one of Asia’s most ill-equipped and under-funded armies.

In addition to fighting decades-long Communist and Muslim insurgencies, the military has come under pressure to acquire more equipment and weapons to defend its territories and claimed areas in the contested South China Sea.

The crashed helicopter was one of six that were delivered in November. The rest of the Blackhawks will be received by the military within a year, Mariano said.