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LOS ANGELES, June 29 (Reuters) - Six people were killed and one was seriously injured on Sunday when two medical helicopters collided on their way to a hospital in Flagstaff, Arizona, air officials said.
The helicopters crashed near Flagstaff at about 3.45 p.m. PDT (2245 GMT), said Ian Gregor, a spokesman with the Federal Aviation Administration in Los Angeles.
Preliminary reports indicated at least one patient was among the three people killed in a helicopter operated by Air Methods Corp (AIRM.O), Gregor said. The other four fatalities, as well as as the injury, occurred aboard a helicopter operated by Classic Helicopter of Utah, he added.
A spokesman for the Flagstaff Police Dept. said two rescue workers were slightly injured in a secondary blast as one of the helicopters on the ground exploded.
"They were treated for minor burns injuries and were released from the hospital in good condition," Sergeant Tom Boughner told Reuters by telephone from the crash site.
Boughner said the two helicopters slammed into a hillside covered with ponderosa pines, leaving a large field of scattered debris and sparking a fire.
The blaze torched about 10 to 15 acres (4 to 6 hectares), but was quickly contained.
Flagstaff lies about 75 miles (120 km) south of the Grand Canyon National Park, one of the largest tourist draws in the United States, which attracts some 5 million visitors a year.
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. (Reporting by Dean Goodman. Additional reporting by Tim Gaynor in Arizona; editing by Philip Barbara)
Two medical helicopters en route to Flagstaff Medical Center reportedly crashed into each other near Flagstaff Arizona, United States, leaving six of the seven passengers dead, and one, a nurse, seriously injured. 

A Bell 407 helicopter on land
At least one passenger of three on a Bell 407 helicopter operated by Air Methods Corp. was reported to be a patient. The other helicopter, also a Bell 407, operated by Classic Helicopters, Ltd., carried four passengers who are all dead except for one with serious injures. Spokesperson Matt Stein of Classic Helicopters said that the patient on board the helicopter they operated was being lifted from a medical emergency on the South Rim of the Grand Canyon.

The helicopters collided at about 3:45 pm PDT (22:45 UTC), according to the Federal Aviation Administration (FAA), and crashed about half a mile (800 metres) from the hospital. The helicopters crashed into a forested hillside, igniting a fire that burned about ten to fifteen acres (four to six hectares) of land, but was contained quickly by rescue workers.

Two medical rescue workers were released from a hospital after an explosion of one of the helicopters on the ground. Reuters was told by Sergeant Tom Boughner that "They were treated for minor burns injuries and were released from the hospital in good condition".
Downtown Flagstaff, Arizona

Flagstaff is a city near the centre of Arizona in the United States. The surrounding areas north-east, west, and south-west are lined with hillsides. The city is just south-east of the popular tourist attraction, the Grand Canyon.

Classic Helicopters states that their pilot had over 10,000 hours of experience and this is the first fatal incident they've had. The FAA is performing an investigation of the incident.