MONTREAL (AP) _ Four bombs exploded today at two plants belonging to BioChem Pharma Inc., a pharmaceutical firm credited with developing develop a drug to fight AIDS.

No injuries were reported in the explosions. More than 200 workers were evacuated.

Police did not disclose any motive for the bombings.

Two bombs went off outside BioChem's plant in Montreal. Two others exploded at company headquarters in Laval, north of Montreal.

Laval police Sgt. Denis Thibodeau said the company had received a telephone warning about a bomb.

Police ordered the evacuation in Laval after discovering a suspicious package outside a building. Shortly afterwards, two explosions went off inside the building within 20 minutes of each other.

BioChem Pharma is one of the largest pharmaceutical firms in Canada. Its British-based partner, Glaxo Wellcome, brought the drug 3TC through trials to market and gets the majority of the profits from the drug.