A few moments ago, I spoke to Brad Thavenet, a professional rescue and salvage diver, who has worked both with FEMA and as a trainer for Dive Rescue International.

Thavenet says that the dive operation to recover debris, evidence and human remains in the waters of the Potomac River is complex, complicated by increases and decreases in depth - as the river is an estuary - and by "entanglement hazards".

"That could be miles of cable and wiring, or jagged metal," he explains. "But there are also hazardous materials, such as jet fuel or black and grey [sewage] water from the flight."

Wet weather forecast in the DC area today could complicate matters further, he adds, by causing run-off from local sewage systems.

Thavenet said that a primary challenge is the cold, dark waters of the Potomac River, which he said would reduce visibility to near-zero.

The rescue divers, who are equipped with communications equipment, would often be guided by operators above-water who have access to sonar imagery.

"They'd be doing a lot of it in the dark, basically, because of the flow of the water," he says. "The communications would allow the divers to get some directions, such as 'go to the right'."

"It's crucial to avoid burnout in these situations, both of personnel and equipment," he said.

The CRJ-700 plane was carrying 60 passengers and four crew. The aircraft is a twin engine, medium range jet, Sky Brary says on its website.

The passenger plane is 106ft 1in (32.3m) long, more than double the 50ft 1in (15.27m) US army helicopter.

There were three soldiers on board the helicopter.

DC plane crash: What you need to know published at 12:30 Greenwich Mean Time

12:30 GMT

It’s lunchtime in the UK, and as Washington DC braces for another day of recovery efforts on the Potomac River, here's a look back at what you need to know.

Investigators have recovered the flight data recorder and cockpit voice recorder, known as black boxes, from the American Airlines plane. The recorders will be analysed at the National Transportation Safety Board (NTSB) lab, nearby the site of the crash, according to CBS.

Multiple factors are being considered in the investigation, officials say, as media reports suggest that one air traffic controller was doing the work of two people at the time of the crash.

The names of some of the 67 victims killed in the fatal crash are being released. Including crew members and passengers on the plane, and two of the three crew on board the US army helicopter.

Overnight, recovery efforts were paused due to "difficult conditions" as DC’s emergency services say they expect to work with NTSB to "conduct additional searches and begin operations to salvage the aircraft".

Weather conditions are not expected to be particularly favourable today, BBC Weather's Sarah Keith-Lucas reports.

We'll continue to bring you the latest updates and analysis from our teams in London and Washington DC, stay with us.