The entire city of Niles was without power for approximately 2 1/2 hours Tuesday morning after a transformer exploded near the National Standard plant on Lake Street.

Brian Bergsma, communications director for American Electric Power, said a fire was reported at a privately owned substation adjacent to AEP’s substation on Lake Street around 8 a.m.

The fire, he said, caused a shutdown of the substation that serves the City of Niles.

Bergsma said it was not AEP’s equipment that was affected.

Power was restored to parts of the city around 10:15 a.m. and the whole city was back on line before 11 a.m.

Niles Fire Chief Larry Lamb said what caused the transformer to explode is still unknown.

Local units responding to the fire included the Niles City Fire Department, Niles Township Fire Department, Niles Utilities Department and Indiana Michigan Power.

The power outage did not cause Niles Community Schools to send children home early as the power returned before that decision had to be made.