The plane, operated by CSI Aviation of Albuquerque, New Mexico, was en route to pickup a patient from a hospital when it crashed and caught fire near Chinle Airport at around 12.40pm.
The Navajo Police Department Chinle District, Navajo EMS and Navajo Nation Fire and Rescue Services rushed to the scene, and all four people on board were pronounced dead.
The victims have not yet been identified, but their next of kin have been notified about their untimely passing.
In the meantime, all access to the Chinle Airport is closed as the investigation continues.
The National Transportation Safety Board and the Federal Aviation Administration is also en route to probe what may have caused the fatal collision.
'This is a tragic loss to the families of those onboard and to the medical air and first responder community,' the Navajo Police Department said in a statement.
'We extend our deepest condolences to their family and loved ones during this time.'
