Crews are using the largest crane on the Eastern Seaboard to haul sections of Baltimore’s Francis Scott Key Bridge, which collapsed nearly three weeks ago, amid a race against the clock to locate the remaining bodies and clear the harbor.

The Key Bridge took five years to construct in the 1970s, but now, crews are rushing to dismantle the remnants of the fallen Baltimore landmark. The effort comes as investigators are still attempting to piece together exactly what happened on March 26, when a wayward cargo ship crashed into one of its support structures, causing six construction workers to plunge to their deaths.

Workers are using the Chesapeake 1000, a floating crane with a storied history that includes helping the CIA retrieve part of a sunken Soviet submarine, to remove massive sections, the heaviest so far weighing about 450 tons. But, the work is tedious, dangerous and incredibly complex, leaders of the operation said Monday.

"There’s a lot of debris, there’s rebar, there’s concrete," said Robyn Bianchi, an assistant salvage master on the project. "We don’t know what dangers are down there, so we have to be very methodical and slow with that."

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In the salvage yard on Monday morning, workers disassembled the metal trusses with propane torches. A pair of giant shears sliced them into more manageable pieces.

So far, over 1,000 tons of steel have been removed from the waterway.

Before any pieces of the bridge are removed, divers plunge into the chilly Baltimore harbor to survey the murky underwater wreckage and assess which parts can be safely extracted.

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At the same time, crews are working to remove some containers from the cargo ship Dali, which collided with the bridge, before lifting steel spans off its bow.

"It presents a dynamic hazard," said Joseph Farrell, CEO of Resolve Marine, which is working on retrieving the ship. He said once that happens, the Dali will return to the Port of Baltimore. "Getting it out of there is a priority."

Four bodies have since been recovered and salvage crews are hoping to recover the two remaining bodies once more of the debris has been removed.

They’re also working toward their goal of opening a temporary channel later this month.

The channel would allow more commercial traffic to resume through the Port of Baltimore, which has been severely impacted since the March 26 collapse. Officials plan to reopen the port’s main channel by the end of May.

BALTIMORE BRIDGE COLLAPSE: SECOND TEMPORARY CHANNEL OPENED, ROUGH WEATHER SLOWS DEBRIS REMOVAL

The ongoing recovery operation comes as the FBI has opened a criminal investigation into the Francis Scott Key Bridge collapse.

The probe centers on the 985-foot container ship, the Dali, looking at any violations of federal maritime law.

It also has a focus on whether ship personnel may have been aware of any onboard technical or operational issues before the ship left the Port of Baltimore.

In a statement to Fox News Digital, the FBI confirmed the bureau "is present aboard the cargo ship Dali conducting court-authorized law enforcement activity."

Fox News’ Danielle Wallace and The Associated Press contributed to this report.