Bridge collapse: Temporary channel opens for boats working on response

The collapse of the Francis Scott Key Bridge could cost as much as $4 billion, which would make the incident a record shipping insurance loss, according to a Morningstar analysis citied in a new Department of Homeland Security assessment obtained by ABC News.

There are currently seven vessels at anchor awaiting to enter the Port of Baltimore, the document said. Two have been directed to other ports.

Dive operations on Thursday will confirm the ship’s stability and structural integrity so crews can begin to offload the 13 damaged containers, the document said.

The bulk of the hazardous material is located on the stern. Of the ship's 4,700 containers, 56 hold dangerous goods, but there is no threat to the public, the assessment said.

Two containers went overboard during the collision, but they did not contain hazardous materials, the document said.

-ABC News’ Josh Margolin and Aaron Katersky

One of the people on the bridge just before the collapse heard the voice of a first responder calling out for him to move off quickly, Maryland Gov. Wes Moore said.

"The first responders, who, again, really moved heroically, after the first mayday was called, were able to move to both keep additional cars from coming on the bridge and to begin to notify the workers and people on the bridge they need to move off the bridge," Moore said during a press briefing Wednesday.

"One of the survivors who I had the opportunity to speak with, one of the things he mentioned to me was as he was moving off of the bridge -- and literally saw the bridge fall right after he moved off -- it was because it was a first responder who was telling him to move off the bridge," Moore said.

That life-saving notification was made "audibly," although other contact between first responders and workers may have been made by cellphone or radio, Moore said.

Secretary of Transportation Pete Buttigieg plans to meet on Thursday with shippers and supply chain operators, as his office assesses industry impact.

Buttigieg said the meeting was intended to help the DOT create a "coordinated approach" as it seeks to mitigate the disruptions to one of the East Coast's most active ports.

"That said, the Port of Baltimore is an important port," Buttigieg said at the White House on Wednesday. "So, for our supply chains and for all the workers who depend on it for their income, we're going to help to get it open as soon as safely possible."

A hazmat investigator looked into the cargo on the container ship and identified 56 containers of hazardous materials, National Transportation Safety Board Chair Jennifer Homendy said Wednesday evening.

The 56 containers hold 764 tons of hazardous materials that include "mostly corrosives, flammables, and miscellaneous Class 9 hazardous materials, which would include lithium-ion batteries," Homendy said.

Some of the hazmat containers had been "breached," and there has been "sheen" seen on the waterway, which state and local authorities are aware of and investigating, according to officials.

Homendy said it wasn't known how many hazardous containers were in the water after the incident.

There were 23 people aboard Dali at the time of the collision, 21 crew members and two pilots, according to the NTSB chair.

During the briefing, Homedy said the data recorders they have access to are considered basic compared to a commercial plane.

The ship's voice data recorder only captured limited information, she said.

The U.S. Coast Guard provided the NTSB with six hours of data between midnight and 6 a.m. ET upon arrival.

Officials said on Wednesday that the quality of audio from the box "varies wildly" because of the high level of background noise, which will have to be filtered out to improve the audio quality.

They expect to recover 30 days of data from the data recorders, she said.

Addressing the collision, the NTSB said that current data points to a power failure, but they have not confirmed that or a possible reason for the likely power failure.