Rescue teams responding to the 29 January in-flight collision involving a PSA Airlines MHIRJ CRJ700 are battling incredibly challenging conditions as they scour the icy Potomac River at night for survivors.

“The conditions out there are extremely rough for responders. It’s cold. The wind is hard out there,” says a Washington, DC fire official.

He adds that the entire rescue operation is being conducted over water, saying, “The river is a large black spot with no lights on it.”

Divers have been in the water since shortly after the collision, which involved the CRJ700 and a Sikorsky UH-60 Black Hawk. It occurred close to 21:00 local time and apparently sent both aircraft plummeting into the river. The water is cold and divers are working around “pieces of ice”, an official adds.

The crash occurred at low altitude as the CRJ700’s pilots were preparing to land on Ronald Reagan Washington National’s runway 33.

Some 200 responders are involved in the rescue mission, using “boats from throughout the region – police and fire boats,” and working in about 8ft (2.4m) of water, the fire official says.

Washington, DC mayor Muriel Bowser says 64 people were aboard the CRJ700 and three were aboard the UH-60. Bowser declines to say if any people have been found alive, though no survivors have been reported.