A gigantic, barge-mounted crane was moving into place on Friday in the waters off Baltimore as authorities prepared to begin salvaging the wreckage of the bridge that collapsed earlier this week – while investigators are still on board the giant container ship that rammed into the bridge piling, bringing it down.

Federal and state authorities have outlined the enormous task of cleaning up and rebuilding the collapsed Francis Scott Key Bridge in Baltimore, which has left a structure nearly as long as the Eiffel Tower is high strewn across the cargo ship that hit it and in the surrounding water.

Clearing the debris currently blocking Baltimore’s port will take several weeks, with a much longer timeframe needed to rebuild the vital bridge, which fell in seconds after being struck by a container ship early on Tuesday morning.

Police managed to stop traffic from going on to the bridge when a mayday was relayed from the ship that it had lost control shortly before 1.30am local time. But there wasn’t time to alert construction workers on the bridge, who fell into the water when the bridge crumpled.

Six men, who were filling potholes on the bridge, are presumed dead, with a search and rescue effort called off after two of the bodies were recovered because of the wreckage in the area. Two others made it out alive after falling into the frigid water.

The largest crane on the US’s eastern seaboard has been transported to Baltimore so crews on Friday can begin removing the wreckage. The crane, which can lift up to 1,000 tons, will be one of at least two used to clear the channel of the twisted metal and concrete remains once they have been cut into manageable pieces, according to Wes Moore, Maryland’s governor.

“We have a very long road ahead of us,” Moore said. “This is daunting. This is complicated.” Moore added that the cleanup was complicated by the fact that a portion of the bridge is sitting atop the Dali, the vessel that struck it. This, and the material that fell into the water around it, has made it difficult for rescue divers so far.

“We’re talking 3,000 to 4,000 tons of steel that’s sitting on that ship,” Moore said. “These divers have been methodical, they’ve been disciplined, they’ve been courageous, diving in darkness with objects all around them.”

A further consideration for officials is that the Dali was carrying at least 56 containers of hazardous material, some of which fell into the water following the crash. Inspectors from the National Transportation Safety Board have boarded the Singapore-flagged Dali to assess the extent of the spillage.

“It’s a massive undertaking for an investigation,” said Jennifer Homendy, chair of the board. “That’s 764 tons of hazardous materials. Mostly corrosives, flammables, and some miscellaneous hazardous materials.”

Joe Biden has pledged that the federal government will pay for the reconstruction of the bridge, with Maryland already granted $60m in federal funding for the initial cleanup. Reopening a new bridge will probably take several years, even if the port itself can be cleared for shipping in the next few weeks.