According to the Federal Aviation Administration, a mid-air collision occurred at approximately 11:25 a.m. involving two helicopters, an Enstrom F-28A and an Enstrom 280C, near Hammonton Municipal Airport.

Reports confirmed that only the pilots were on board each helicopter at the time of the incident.

Hammonton Police Chief Kevin Friel informed the Associated Press that emergency responders successfully extinguished the fire that had engulfed one of the helicopters.

The helicopters crashed into a field in Hammonton, and both pilots were subsequently airlifted to a trauma center, as reported by Hammonton Fire Department Chief Sean Macri to CNN.

The National Transportation Safety Board has taken charge of the investigation to determine the cause of the crash.

Investigators will likely first look to review any communications between the two pilots and whether they were able to see each other, said Alan Diehl, a former crash investigator for the FAA and NTSB.

“Virtually all midair collisions are a failure to what they call ‘see and avoid’,” Diehl said.

“Clearly they’ll be looking at the out-of-cockpit views of the two aircraft and seeing if one pilot was approaching from the blind side.”

Although it was mostly cloudy at the time of the crash, winds were light and visibility was good, according to the weather forecasting company AccuWeather.

Hammonton, located in Atlantic County, is about 56km from Philadelphia and sits near the New Jersey Pine Barrens, a vast area of forested wilderness.

The Hammonton Fire Department has asked bystanders to avoid the area while emergency services respond to the incident.