Authorities are keeping a close eye on a cargo ship that collided with a bridge in Baltimore. The vessel is carrying 1.8 million gallons of fuel and other dangerous substances.

BALTIMORE, Md. — Federal officials are monitoring about 1.8 million gallons of fuel inside the container ship Dali for its “spill potential,” according to an unclassified memo from the federal Cybersecurity and Infrastructure Security Agency. But a U.S. official familiar with the matter told CNN “lots would have to go wrong” for that amount of fuel to spill.

The Department of Homeland Security has also deemed the water near the crash site unsafe for divers, according to a memo obtained by ABC News.

The concerns come after the vessel struck Baltimore’s Francis Scott Key Bridge Tuesday morning, causing a near-total collapse.

A search-and-rescue effort for six people believed to have fallen from the collapsing bridge into the frigid waters of the Patapsco River below has been suspended and will shift to a recovery mission, officials said.

An elite Coast Guard team is examining 13 damaged containers, “some with Centers for Disease Control and Prevention [CDC] and/or hazardous materials [HAZMAT] contents,” the CISA memo said. The team is also analyzing the ship’s manifest to determine what was on board and if any materials could pose a health risk, the source said.

“There is minor sheening on-scene. Booming has been ordered and is staged but will not be placed until search and rescue and dive operations are complete,” the document said. “The amount of potential oil spill is 1.8M gallons of marine grade diesel.”

Imagery from underwater drones show “an abundance of twisted metal and debris” from the collapsed bridge, making it unsafe for divers to enter the frigid water to search for the six missing construction workers, the DHS assessment added.

Maryland Gov. Wes Moore called the collapse a “catastrophic and horrific occurrence” for the state and the families of those missing, who he was able to speak with Tuesday.

“They reminded us who these individuals were – that they weren’t just special workers who were doing important work for the city and for the state, but they were people who were husbands and sons and fathers and brothers-in-law,” Moore said. “So, this is a really devastated community of families.”

One truck and trailer have been recovered, and one vehicle remains hanging from the metal structure, according to DHS.

With the Port of Baltimore closed to maritime traffic, transportation officials expect backups to rail and truck freight shipments as cargo shifts along the eastern seaboard, the document said.

NTSB investigators, who are leading the investigation, arrived at the bridge scene at 6 a.m. on Tuesday. Twenty-four NTSB staffers were on site, including several specializing in nautical operations, human performance and engineering, NTSB chairwoman Jennifer Homendy said Tuesday.

She said on Wednesday that those investigators were expected later in the day to board Dali, the vessel that crashed into the bridge.

“We aren’t looking at the structure today,” she said, meaning the fallen bridge. “We will be boarding the vessel at some point today to begin to look at the devastation really, and then look through the vessel itself. “

Questions over previous incidents involving ship and management company

As officials worked to investigate the collapse Tuesday, questions emerged over previous issues with the ship and its management company.

The ship was briefly held at the Port of San Antonio in Chile on June 27, 2023, when an inspector found that the pressure gauges for the vessel’s heating system were “unreadable,” a spokesperson for the Chilean Navy said.

Ships managed by the Synergy Marine Group have been involved in at least three deadly incidents since 2018 in Australia, Singapore and the Philippines, according to officials in those countries.

In 2018, a member onboard of a vessel managed by Synergy in Australia was killed in an accident involving the ship’s personnel elevator, according to a report from the Australian Transportation Safety Bureau.

In 2019, an officer on a Synergy-registered vessel in Singapore was reported missing after “likely (falling) overboard while performing inspection or cleaning jobs,” according to a report by the Transport Safety Investigation Bureau of Singapore’s Ministry of Transport.

In 2023, at least one sailor was killed when a Synergy Marine-managed tanker collided with a dredging ship in the Philippines, causing it to capsize, according to an incident report from the Philippines Coast Guard.

CNN contributed to this post.