LOS ANGELES - Four cargo ships, stuck for about a month at the Port of Baltimore by the ruins of the collapsed Francis Scott Key bridge, have exited this week via a temporary channel, according to shipping data.

Large ship traffic to and from the port, the busiest in the U.S. for auto shipments, has been severely restricted since the hulking Dali container ship lost power and smashed into the bridge on March 26, bringing it down and blocking the channel. The FBI has launched a criminal probe into the incident, which killed six bridge workers.

The Balsa 94, a general cargo carrier, on Thursday was the first to exit Baltimore Harbor via a new channel that is 300 feet (91 meters) wide and at least 35 feet (11 meters) deep. That Panama-flagged vessel, which had been at the Baltimore port since March 23, is now en route to Saint John, Canada, according to LSEG data.

Other exiting ships were the Saimaagracht, a Netherlands-flagged general cargo ship, the Carmen car carrier owned by Norwegian/Swedish shipping firm Wallenius Wilhelmsen and the Thailand-flagged bulk carrier Phatra Naree.

The Dutch-flagged Frisian Ocean, a general cargo ship, was among the vessels that used the new channel to enter the port before it temporarily closes on Monday so workers can remove the Dali.

"We're working to strike a balance between enabling temporary access to support commercial activity and undertaking necessary measures to fully reopen the Fort McHenry Channel," said U.S. Coast Guard Captain David O'Connell, the federal on-scene coordinator for the Key Bridge response team.

The reopening of the port's main channel remains on track for the end of May, officials said.

During the first nine months of 2023, the Port of Baltimore was the second-biggest port for U.S. coal exports, behind Norfolk, Virginia.

Coal piled up at terminals before new shipments were diverted, kicking up dust, residents told Reuters. Two coal carriers, the JY River and Klara Oldendorff, remain stranded at the port.

Some barges carrying agricultural goods, coal and metals will continue to have access to the port via a more shallow channel that opened during the weekend. Domino Sugar Baltimore said on the X social media site that the barge the Jonathan is again delivering raw sugar for its refinery.

(Reporting by Lisa Baertlein in Los Angeles; Editing by Bill Berkrot)