The blasts struck at the shipyard in the Caribbean port of Cartagena, where police were "investigating whether it was an accident or an attack," a source in the force told AFP.
"There were three explosions, two of them at the same spot," a spokeswoman for the local fire service said.
She said two of the blasts struck US shipbuilder Astivik. The third rocked the premises of Colombian naval corporation Cotecmar.
Authorities did not immediately clarify how many died at each site.
Firefighters put out blazes caused by the explosions, the spokeswoman told AFP.
The shipyards lie in an industrial zone some 15 kilometers (nine miles) from the tourist center of Cartagena.
Cotecmar's president Jorge Enrique Carreno told reporters one of the blasts was in a tanker vessel that was undergoing maintenance.
Officials speculated that the blast may have been caused by the ignition of gas inside vessels in the shipyard.
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