Six people died and three were injured after two medical helicopters collided Sunday on their way to a hospital in Flagstaff, Arizona. The accident occurred just east of Flagstaff Medical Center, near a mesa, at approximately 3:45 p.m. local time, according to Ian Gregor, a spokesperson for the Federal Aviation Administration.

At least one of the three people killed aboard the plane operated by Air Methods Corp, an air medical service provider headquartered in Englewood, Colorado, was a patient. The other three deaths, as well as one of the injuries, took place aboard the other helicopter operated by Classic Helicopter of Woods Cross, Utah. The other victims are two rescue workers who were slightly injured when the helicopter on the ground exploded. The blast set off a blaze that destroyed 10 to 15 acres before being contained by on the scene firefighters.

"They were treated for minor burns injuries and were released from the hospital in good condition," said from the crash site Sergeant Tom Boughner, representative for the Flagstaff Police Dept., as quoted by Reuters.

Boughner also said that the copters crashed into a wooded area near a neighborhood and that no person on the ground was believed to have been injured or killed in the crash.

At the time of the crash, both of the Bell 407 choppers were headed to the Flagstaff hospital, Ian Gregor said.

Classic Helicopters’s crew was landing at the hospital carrying a patient from the Grand Canyon’s South Rim, said Matt Stein, a company spokesman. He said the helicopter’s pilot, paramedic and patient were all killed. A flight nurse was in critical condition at Flagstaff Medical Center. Stein said the pilot was experienced, having more than 10,000 hours of flight time.

Four people were killed in a similar accident in Arizona last year, when two news television helicopters collided while following a car chase in Phoenix.

Flagstaff lies about 75 miles (120 km) south of the Grand Canyon National Park, one of the biggest tourist attractions in the United States, which registers around 5 million visitors a year.