Paris, Feb 9 (IANS): Five persons were injured in an explosion and fire at a nuclear power plant in northern France on Thursday, but no radiation was released from the plant, according to the power utility company that operates it.

The explosion was reported at an Electricite de France (EDF) nuclear power plant in Flamanville on the Normandy coast, Efe news reported.

"Flamanville 1, a fire was controlled in a non-nuclear zone," EDF said on its official Twitter account. "No casualties and no consequences for safety and the environment," the energy giant added.

According to the EDF Flamanville's website, the incident took place at 9:45 a.m. in the engine-room of reactor number 1, that has been in service since 1986. The reactor was automatically shut down and switched off the national grid in accordance with safety protocols.

The prefect of La Manche, Jacques Witkowski declared the incident as "over."

Although the cause was not yet known, an overheated ventilation system in the engine room appeared to have caght fire and affected a transformer that exploded.

The transformer's electrical insulation provoked a fire that belched thick clouds of smoke, but there was no radiation risk involved, Witkowski said.

A technical inquiry will examine the causes of the incident, he said.