Four residents at a retirement home in southern France have died and over a dozen others were sickened in a suspected case of food poisoning, officials said Monday.

Twenty-two people at the Cheneraie residence in Lherm, a town south of Toulouse, began showing symptoms including vomiting after dinner on Sunday, police said in a statement. 

Fifteen of the 82 residents at the home remained in serious condition.

The meals involved have been kept for analysis, the regional health agency said, and residents were being questioned about what they ate.

"We suspect food poisoning because these events occurred after the meal," deputy prosecutor Marie-Paule Demiguel told BFM television, adding that the kitchens at the residence would also be investigated.

The site, open since 2006, operates under licence from the French government but is run by the private firm Korian, which claims to be the largest network of retirement homes in Europe, with over 800 sites in five countries, representing 78,000 beds.