MONTREAL - Hydro-Quebec CEO Thierry Vandal has resigned after nearly a decade at the helm of the power utility.

Vandal, who is in his mid-50s, will leave the government-owned utility May 1. No reason was given for his resignation.

In October, the provincial government appointed Montreal businessman Michael Penner as Hydro-Quebec's chairman, replacing Pierre Karl Peladeau, who left to enter politics.

Penner, who praised Vandal for making made a "striking contribution" to the development of Hydro-Quebec, said the board will decide in the coming weeks on a replacement process.

Vandal, an engineer, joined Hydro-Quebec in 1996, serving as vice-president strategic planning and later president of production. He came from the petroleum and natural gas sectors, having worked at Shell Canada, Kemtec Petroleum and later Gaz Metro.

Vandal is a past chairman of the Conference Board of Canada and sits on the board of McGill University and the University of Montreal's HEC business school, from which he has an MBA and honorary doctorate.