A series of fires that lit up the night sky over the Mobile River in Alabama Wednesday night burned themselves out this morning, leaving three people injured in their wake.

The fires were set off by a series of explosions aboard fuel barges that began around 8 p.m. Wednesday, according to Lt. Michael Clausen with the U.S. Coast Guard.

The cause of the explosions is still under investigation but authorities believe they could have been started by a spark or ignition source that ignited gasoline vapors within the barges.

The three injured, all personnel aboard the barges, were taken to the University of South Alabama Medical Center with burn-related injuries. All three remain hospitalized, one in critical condition, according to Clausen.

Following the first explosion, the Coast Guard established a one-nautical-mile safety zone around the barges, identified by Clausen as empty natural gas barges docked for cleaning at the time of the explosions. The barges are owned by Kirby Inland Marine, a Channelview, Texas-based company that describes itself as operating, "the nation's largest fleet of inland tank barges and towing vessels."

The Mobile Fire and Rescue Department sent in a hazardous materials team to check for any dangerous chemicals aboard the barges, but determined today that "no further hazards exist," according to the department's Twitter feed.

The explosions and fires also led to the evacuation of Carnival Cruise Lines' the Triumph, the same ship that was stranded in the Gulf of Mexico two months after suffering an engine room fire with passengers aboard. The evacuation of the ship, docked nearby while undergoing repairs, was a self-evacuation by Carnival, not under the Coast Guard or fire department's command, according to Claussen.