New sonar images of Francis Scott Key wreckage reveals look of the mangled bridge 50 feet below the Patapsco River

US Navy divers have secured new sonar images of the wrecked Francis Scott Key Bridge, swimming into 'virtual darkness' inside murky clouds of displaced river mud.

Their sonar captured the deepest remains of the infamous bridge collapse from the lowest point of Baltimore's Patapsco River federal shipping channel - 50 feet below the water's surface.

The new look of the wreckage below the depths shows the metal framework slumped below the mudline, which officials said would be more difficult to salvage.

The Navy has provided three barges, at a combined lifting capacity of 1,350 tons, with another 400-ton capacity barge on route, for the clean-up and salvage effort.

US Navy divers swimming in 'virtual darkness' through murky plumes of displaced river mud have secured new sonar images of the wrecked Francis Scott Key Bridge. The bridge's submerged metal frame extends above the waterline, visible as a blue line in the sonar images

Their sonar captures the deepest remains of the infamous bridge collapse from the lowest point of the Baltimore's Patapsco River's federal shipping channel, 50 feet below the surface 

Government agencies are now racing to clear the Key's mangled steel trusses and remove the grounded, 984-foot cargo ship, the Dali, which smashed into the bridge on March 26 (above) - killing six construction workers and laying waste to the vital commuter bridge 

Army Corps of Engineers Col. Estee Pinchasin said during press conference this month: 'Surveys are indicating the wreckage on the bottom of the 50-foot channel is far more extensive than we could have imagined.

'It’s not just sitting on the seabed, it’s actually below the mud line. That makes it very difficult to know where to cut and how to cut, and how to rig and lift.'   

The Navy joins state, local and federal agencies now racing to clear the Key's mangled steel trusses and the grounded, 984 foot-long cargo ship, the Dali, which smashed into the bridge on the morning of March 26 — killing six construction workers as it laid waste to the critical commuter bridge. 

Government officials hope to carve out a makeshift shipping lane by the end of April: a smaller 280-foot-wide and 35-foot-deep channel which they hope will restore commercially vital activity back to the Port of Baltimore. 

The sonar dives, which use the 3D underwater sonar imaging tool named CODA Octopus, are key to the essential, but painstaking phase of identifying and locating all of the bulk debris that was once the Francis Scott Key.

'Despite the CODA footage that we're using […] it still takes time,' said Captain Sal Suarez, the Navy's supervisor of salvage and diving, in a video last week.

Government officials hope to carve out a small, makeshift shipping lane by the end of April: a 280-foot-wide and 35-foot-deep channel that they hope will restore commercially vital activity back to the Port of Baltimore. Above, more new sonar imagery released Wednesday

Haunting satellite images show the aftermath of the Francis Scott Key Bridge's destruction after being struck by a 105,000 ton shipping container

EXCLUSIVEREAD MORE: Engineers blame $3m structural 'flaw' for Baltimore's Francis Scott Key bridge collapsing - and tens of thousands of bridges across US could also have fault

No bridge can withstand millions of pound of force from a strike, as with the cargo ship that hit the Francis Scott Key Bridge. 

CODA Sonar images of the wreckage began trickling in over the course of early April as the dive team's first mapped the wreckage in shallower depths of the river.

Visibility for the divers reaches just 'one to two feet' ahead of their eyes, according the Army Corps of Engineers, because of the four to five feet of mud and loose silt kicked up after the bridge wreckage's impact with the bottom of the Patapsco River. 

'Divers are forced to work in virtual darkness, because when lit, their view is similar to driving through a heavy snowfall at night with high-beam headlights on,' a spokesman with the corps posted to Facebook.

'So murky is the water, divers must be guided via detailed verbal directions from operators in vessels topside who are viewing real-time CODA imagery.' 

The dive teams are recording no underwater river footage themselves because, as one Navy-led diver put it, 'There's no need take video of something you can't even see.'

Laser-based 'Light Detection and Ranging' or LiDAR is also in use by supervisors on land, to better provide the divers in the water with situational awareness of the tangled, and clouded wreckage lidar, Capt. Suarez said at a news conference last Thursday. 

Capt. Suarez and his 20-person team have also been tasked with assessing the damage to the Dali, as part of their emergency contract.

'You're limited by how much time you can spend on the bottom depending on the depth for each diver,' Capt. Suarez, who is officially the director of ocean engineering for US Naval Sea Systems Command (NAVSEA), said.

'You're also limited by the safety factor,' he explained. 'This is wreckage in all sort of shapes and sizes and it's dangerous.'

Currently, no active-duty Navy divers are part of the salvage project, despite the Navy personnel leading the effort. 

Since the bridge's collapse on March 26, at least  135 Navy personnel, two utility boats, a ridged hull inflatable boat, several tugboats, and 12 crane and support vessels have all headed to the Patapsco to aid in the salvage and clean-up operation.

Salvage teams also began removing mangled containers from the deck of the Dali cargo ship this week, from where the massive vessel remains pinned beneath the wreckage of the Francis Scott Key.

The Dali's 22-man crew from India has spent nearly two weeks stranded on board, with it unclear when they will be able to disembark the ship which had been only minutes into a 28-day journey when it lost power and crashed.

The crew is unharmed and has been provided with food, water, and fuel supplies, according to the New York Times.

The removal of containers from the deck of the Dali is set to continue this week as weather permits, according to the Key Bridge Response Unified Command.

'The Limited Access Channel will permit larger ships in and out,' the US Army Corps of Engineers Baltimore District office said in a statement on social media Wednesday.

Marine tugs, Maritime Administration (MARAD) boats, and cargo vessels used for 'Roll-on/Roll-off' shipping, which move automobiles and farm equipment, will be among those cleared for the temporary, more shallow channel.

The Army Corps of Engineers said it has set an 'ambitious' but tentative deadline to fully clear and restore channel access to the Port of Baltimore by the end of May.