Jul. 2, 2009 (United Press International) -- Animal rescue workers in the Canadian border city of Windsor, Ontario, say they suspect poisoning in the deaths of 100 seagulls found atop a vacant store.

Nancy Phillips, president of Wings wildlife rehabilitation center, told the Windsor Star a phone caller tipped off the group about the colony living on the roof of a former Home Depot (NYSE:HD) store.

She estimated there are as many as 400 gulls in the colony, many of them sick and starving.

"There's got to be something on the roof," she said. "They eat it, swell up, get all poisoned inside and can't drink or eat."

The group rescued about 45 gulls, but Phillips said not all of them were expected to survive.

Melanie Coulter, executive director of the Windsor-Essex Humane Society, told the Star putting out poisoned food isn't necessarily illegal in Ontario.

"If it's considered pest control, it's not illegal," she said. "Under the animal protection legislation, there's not much we can do."