Two pilots have died after their helicopters collided mid-air on Sunday above a city in New Jersey, police said.

Hammonton Police identified the pilots as Kenneth L. Kirsch, 65, and Michael Greenberg, 71, both of New Jersey, according to a BBC news partner, CBS.

Only the pilots were on board each aircraft, the Federal Aviation Administration (FAA) stated in a statement, adding there would be a federal investigation into what led to the collision.

Hammonton is about 35 miles (56km) southeast of Philadelphia, Pennsylvania, just off the Atlantic City Expressway.

Police on Sunday reported that one of the helicopters was engulfed in flames by the time it crashed and landed on the ground, and emergency services were working to extinguish the fire.

According to the National Transportation Safety Board, the crash involved an Enstrom 280C helicopter and an Enstrom F-28A helicopter and happened at around 11:25 EST (16:25 GMT). Both helicopters are lightweight aircraft that typically hold three people or fewer.

In January, a military helicopter collided with a passenger jet in Washington, DC, killing 67 people.

FAA data shows that the rate of deadly helicopter accidents has fallen on average over the last three years.