Four people have been confirmed dead following a devastating medical aircraft crash in Arizona.

Emergency crews from Navajo Police Department Chinle District, Navajo EMS and Navajo Nation Fire and Rescue Services raced to the scene of the medical plane crash at 12.40 pm on Tuesday.

The National Transportation Safety Board and the Federal Aviation Administration will probe what triggered the fatal incident. The four victims aboard the aircraft have been identified but are yet to be publicly named, though police confirm their relatives have been informed.

The Navajo Nation President has confirmed the aircraft was travelling to collect patients when it plummeted from the sky, with the police department stating that the victims were not local. This is the second deadly small plane crash in recent days, with it emerging last week that a 13-year-old boy had died in an air accident while in Majorca.

CSI Aviation, an Albuquerque, New Mexico-based firm, operated the aircraft, which was a Beechcraft 300 model - a compact twin-propeller medical transport vessel.

The plane was heading towards the hospital when it plunged and burst into flames near Chinle Airport this afternoon, roughly 200 miles (321 kilometres) northeast of Flagstaff.

"This is a tragic loss to the families of those onboard and to medical air and first responder community," the Navajo Police Department declared in a statement.

Navajo Nation President Buu Nygren expressed his devastation over the crash in a social media message.

"These were people who dedicated their lives to saving others, and their loss is felt deeply across the Navajo Nation," he said.

"The four were enroute to pick up a patient when the plane crashed around 12:40 p.m. this afternoon. We honor their service, their sacrifice, and the love they showed our communities through their work. On behalf of the Navajo Nation, I extend my deepest condolences to their families, colleagues, and all who are grieving," Nygren added.

"Our prayers are with the families of those on the plane as investigations continue. May the Creator bring comfort and strength in the days ahead," the statement concluded.

The airport has been shut while an investigation is carried out.