Three American firefighters were killed when their tanker plane crashed battling wildfires in Australia on Thursday. Officials in New South Wales confirmed the crash and the fatalities. It was also confirmed in this social media post from Coulson Aviation.

New South Wales Premier Gladys Berejiklian offered her condolences to the families of those that were killed. She stated that flags in New South Wales would be flown at half staff in honor of the deceased on Friday.

Australian Transport Safety Bureau, the national air crash investigator, and state police will investigate the crash site, which firefighters described as an active fire ground.

Coulson Aviation has also announced that its fleet of firefighting aircraft has been grounded pending the outcome of an investigation into the crash. The C-130 air tanker was one of several aircraft deployed by Coulson Aviation to aid Australian authorities in battling the blazes which have now taken 31 lives since they began last year.