SYDNEY (AP) — A tanker plane that crashed and killed its three American crew members as they fought wildfires in Australia had just dropped liquid to suppress the flames, investigators said Friday.

The crash Thursday killed Capt. Ian H. McBeth, 44, of Great Falls, Montana; First Officer Paul Clyde Hudson, 42, of Buckeye, Arizona; and Flight Engineer Rick A. DeMorgan Jr., 43, of Navarre, Florida, their employer, Canada-based Coulson Aviation, said in a statement.

The deaths came during an unprecedented wildfire season that has left a swath of destruction in Australia’s southeast. More than 30 people have died, including three Australian volunteer firefighters.

Investigators went to where the C-130 Hercules tanker crashed in the Snowy Monaro region of the state of New South Wales, and a team was working to recover the Americans’ bodies, Australian Transport Safety Bureau Chief Commissioner Greg Hood told reporters.

He said it would be difficult to secure evidence and the remains because the wildfire is still burning and the team faces potential hazards such as aviation fuel.

Upward of 500 aircraft from several countries are fighting Australia’s wildfires, Hood said.

ìSo, if there are lessons to be learned from this particular accident, it’s really important that not only Australia learns these, but the world learns them,î he said.

A memorial service will be held Feb. 23 in Sydney for the U.S. and Australian firefighters who have died this wildfire season, New South Wales Premier Gladys Berejiklian said.

“We will pay tribute to the brave firefighters who lost their own lives protecting the lives and properties of others,” she said.

The three U.S. deaths brings the toll from the blazes to at least 31 since September. The fires have destroyed more than 2,600 homes and burned more than 40,000 square miles, an area bigger than the U.S. state of Indiana.