Washington, March 11 (IANS/EFE): Seven marines and four other US soldiers were reported missing after an Army helicopter crashed during a routine exercise in the south-eastern state of Florida.

US media reported that the accident took place outside the Eglin Air Force Base in Florida's north-western region.

The missing marines were part of a Camp Lejeune-based special operations group in North Carolina, while the other soldiers are from a Hammond, Louisiana-based National Guard unit, said official US sources.

The helicopter was reported missing by the authorities on Tuesday night at 8.30 p.m., while rescue teams found the wreckage about six hours later.

Apparently, the plane crashed during a routine training manoeuvre on a beach stretch between Pensacola and Destin, an area commonly used to conduct military exercises.

A spokesperson for the Eglin Air Force Base, Andy Bourland, told the US NBC Television Network that search and rescue operations were still underway and that it was too soon to say what caused the crash; however, there had been "weather issues" during the night.

Bourland added that visibility was limited due to darkness and fog.