A tugboat pushing a fuel barge became the first vessel to sail through a temporary channel opened beside the collapsed Francis Scott Key Bridge in Baltimore harbor, authorities overseeing the cleanup operation said late Monday.

Two small, temporary channels are being opened for ships helping clean up the site of the catastrophe.

Officials said the channels would initially only be open to smaller vessels involved in the cleanup operation, and would not be big enough to allow cargo and container ships to pass through.

The tugboat Crystal Coast pushing a fuel barge transited the first temporary channel at 3:00 pm Monday (1900 GMT Monday), becoming the first vessel to transit since the bridge collapsed last Tuesday after being struck by an out-of-control cargo ship.

The barge was used to supply jet fuel to Dover Air Force Base for the Department of Defense, the joint information center for the agencies overseeing the cleanup operation said in a statement.

A second, slightly deeper channel will be opened in the coming days, Maryland governor Wes Moore told reporters.

The opening of the temporary route "will help us to get more vessels in the water around the site of the collapse," he told a press conference.

This will allow more workers to pitch in toward the mammoth task of clearing the harbor of the bridge, which was destroyed in seconds last Tuesday when the Singapore-flagged Dali lost power and hit a bridge support column, killing six people.

Shipping in and out of Baltimore -- one of the United States' busiest ports -- has been halted, with the waterway impassable due to the sprawling wreckage.

The authorities hope that removing the bridge -- by cutting it into smaller sections and lifting them out -- will help rescuers recover all the victims' bodies and eventually reopen the crucial shipping lane.

On Friday, President Joe Biden is due to visit the port city, which is about 40 miles (64 kilometers) north of Washington, the White House announced.

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The first temporary channel has a depth of at least 11 feet (3.4 meters), a 264-foot horizontal clearance and vertical clearance of 96 feet, the multi-agency task force overseeing the operation said in a statement.

This temporary channel "is not big enough for any container or cargo ships to pass through," US Coast Guard petty officer Carmen Caver told AFP.

"They're working on a plan to make it slowly open to more and more people," she added.

Work was underway on opening a second channel which would allow larger vessels with a draft 15 to 16 feet, the multi-agency task force overseeing the operation said.

The port of Baltimore is a key hub for the auto industry, handling almost 850,000 autos and light trucks last year -- more than any other US port -- according to Maryland state figures.

It also ranked first for farm and construction machinery, as well as imported sugar and gypsum, and second for coal exports.

The operation to recover the missing bodies and to reopen the port to larger vessels has been hampered by the challenge of diving around the structure, according to Moore.

"We're talking about water that is so murky and so filled with debris that divers cannot see any more than a foot or two in front of them," he said.

"We have to move fast, but we cannot be careless," he added.