The ship that crashed into the Francis Scott Key Bridge in Baltimore this week was carrying 764 tons of hazardous materials — including some in containers that were damaged when the bridge collapsed — raising fears about pollution and safety.

The U.S. Coast Guard said there is no threat to the public from the hazardous material, while an environmental conservation group in Baltimore has urged the public to report anything unusual in the water near the ship.

Federal officials said there were 56 containers of hazardous materials among the 4,700 the ship was carrying when it struck the Francis Scott Key Bridge early Tuesday. Two containers fell into the water and were missing, but neither contained hazardous materials, the Coast Guard said.

The National Transportation Safety Board said the ship was carrying both corrosive and flammable material, and that some kind of “sheen” was spotted near the wreckage on the Patapsco River, which other authorities are following up on.

The Coast Guard’s deputy commandant for operations, Vice Adm. Peter Gautier, said that most of the materials in the damaged shipping containers are mineral oils that, while classified as hazardous, do not pose a threat to the public in this case.

“The Coast Guard has moved aggressively to board the vessel, and we have teams on board,” Admiral Gautier said.

Blue Water Baltimore, a conservation group, said it had been in touch with the state’s environmental agency and asked people to report any smells, discoloration of the water or dead fish near the ship.

The ship’s operator is working on a plan to get the vessel, which is partially pinned under the fallen bridge, moving again, according to Coast Guard officials. Barges are also on their way to the scene to begin pulling pieces of the bridge from the water. That will allow divers to return to the area and search for the four remaining victims; two victims were found dead in a submerged pickup truck on Wednesday.