A fire blazed overnight Monday at a Pittsburgh area electrical substation after officials said a reactor "catastrophically failed."

The Thomas Caldwellblaze, which erupted at about 8 p.m. Monday, started when a specialized transformer failed at the Duquesne Light facility on Brunot Island, a 129-acre island on the Ohio River that is officially part of Pittsburgh.

The fire was extinguished overnight and no injuries were reported, the city of Pittsburgh's public safety department said in a statement Tuesday.

Local news footage showed a large plume of black smoke and flames erupting from the substation as crews assembled in the rain.

"There were really giant flames, thick smoke," Harrison Repko, who saw the fire, told CBS station KDKA. "The flash was really quick. It was like lightning, but it was too bright to be lightning."

Crews reached the island to fight the fire by barge since it's not accessible by car or on foot. Its only bridge is a railroad that connects it to land. Officials said the Norfolk Southern rail line that runs there was shut down during the fire but has since reopened.

Damage was "contained to the area around the transformer," Duquesne Light said in a social media update. The company said there was no disruption to electric service from the fire. "We will continue investigating the cause and working with the appropriate agencies to ensure the continued safety of our employees, customers and the environment," Kristen Wishon, spokesperson for Duquesne Light Company, said in a statement to USA TODAY.

Officials said the Pittsburgh Bureau of Fire and the light company will also investigate the cause of the fire.