Mobile Fire Chief Steve Dean said that for safety reasons firefighters were keeping a distance from the barges, which were carrying raw gasoline and had already been the source of multiple explosions.
The barge explosions forced the crew of Carnival Corp's cruise vessel Triumph to evacuate.
"Everybody is just monitoring the situation right now," Dean told reporters.
Three people with a team servicing the barges were injured and transported to Mobile's University of South Alabama Medical Center, Mobile Fire and Rescue Department spokesman Steve Huffman said. A hospital spokesman said separately that they were all in critical condition.
The barges were carrying raw gasoline, Huffman said. Fire officials had originally said the barge explosions involved natural gas.
Huffman had no information on who owns the barges or what was their destination.
The cause of the explosions was unknown and would not be determined until after firefighters reached the vessels, he said.
Carnival Corp's Triumph previously made headlines in February when an engine fire left it and 4,000 passengers adrift in the Gulf of Mexico, until they were towed back to land.