(CNN) -- A fire that sparked huge explosions and injured three workers on a pair of Mobile River barges is out, the U.S. Coast Guard said Thursday.
Three workers who were preparing the barges for reloading Wednesday night were severely burned, according to Mobile fire officials.
They were in critical condition Thursday at the University of South Alabama Medical Center, according to a spokesman. Authorities don't believe any workers are missing.
The barge was empty at the time of the initial explosion Wednesday night, but authorities believe a spark ignited vapors in it, causing an explosion that ignited a second barge, CNN affiliate WALA TV reported, citing Coast Guard Lt. Mike Clausen.
At least seven explosions rocked the barges, according to the Coast Guard.
At the Fort Conde Inn across the river they sounded like "planes above you dropping bombs," general manager Alan Waugh told WALA Wednesday.
"We were up on a second floor balcony and the sky lit up in orange and yellow," he said.
With the fire out, the Coast Guard has lifted the safety zone around the scene, allowing the shipping channel to reopen, the agency said in a news release.
The barges are moored across the river from the Carnival Triumph, the cruise ship that lost power in February and drifted in the Gulf of Mexico for days before being towed to Mobile for repairs.
At least 500 employees working on the ship were evacuated, Huffman said.
CNN's Chuck Johnston, Michael Pearson, Tina Burnside, Dave Alsup, Jessica Jordan, Greg Botelho and Chandler Friedman contributed to this report.