Fire officials said they planned to let the barges burn into the night because the situation was too unstable.
The Carnival Triumph, the cruise shop that became disabled in the Gulf of Mexico last February before it was towed to Mobile's port, was evacuated, the Mobile Press-Register reported.
The explosions happened in an area of the river east of downtown Mobile, Huffman said. U.S. Coast Guard Petty Ofc. Carlos Vega said the initial blast took place in a ship channel near the George C. Wallace Tunnel which carries traffic from Interstate 10 under the Mobile River.
The explosions rattled the windows of houses in downtown, blew doors open in the Spanish Fort area and aftershocks were reported in Bay Minette and Fort Morgan, the Press-Register reported. Video from WALA-TV shows flames engulfing a large section of the barge.
Coast Guard officials were heading to the scene and the cause of the explosion was not immediately clear, Vega said.
The explosion comes two months after the 900-foot-long Triumph was towed to Mobile after becoming disabled during a cruise by an engine room fire, leaving thousands of passengers to endure cold food, unsanitary conditions and power outages. The ship is still undergoing repairs there.
Earlier this month, it was dislodged from its mooring by a windstorm that also caused two shipyard workers to fall into Mobile Bay. While one worker was rescued, the other's body was pulled from the water more than a week later.