Four people were killed when the medical transport plane they were in crashed at an airport in the Navajo Nation in the US state of Arizona, police said.

The small dual-propeller plane crashed and burned at Chinle Airport at approximately 12:40pm. There were four people on board, none of whom were local residents, and they were confirmed dead, according to the respective press release.

The plane was en route to a hospital to pick up a patient.

Representatives from the US National Transportation Safety Board and the Federal Aviation Administration have arrived at the scene to investigate the crash.

The cause of this plane crash is still unknown.