A fire caused the shutdown of a nuclear reactor in eastern Belgium on Sunday, media reports said, making it the fourth reactor to go offline in the country.

The reactor near Liege is one of seven operated by Electrabel, a subsidiary of France's GDF Suez.

The fire "happened outside the nuclear zone," said mayor Alexis Housiaux of the adjoining town of Huy.

Electrabel said the fire at the Tihange 3 reactor was brought under control around midday, and that there had been "no impact on nuclear safety and the safety of the workers and the residents near the site."

A preliminary investigation ruled out sabotage -- the cause of a shutdown at another plant in August -- concluding that the fire had a "technical cause".

Two other nuclear plants, in Antwerp and Tihange, have been shut since March following the discovery of micro-cracks in them.

Both had previously halted operations between June 2012 and June 2013.

Some 55 percent of Belgium's electricity is nuclear.