A second child poisoned by a dangerous insecticide in a Fort McMurray, Alta., apartment has died.

The death of the two-year-old boy was announced on Thursday by an imam at the funeral for the family’s eight-month-old daughter.

The baby girl died and her four siblings were sent to hospital in critical condition on Sunday after their mother tried to kill bed bugs in the family’s apartment with a deadly fumigant she brought back from Pakistan.

Allan Vinni, the lawyer for the family, identified the boy as Zia-Ul Hasan Syed, his father as Syed Habib and the mother as Nida Habib.

Taj Mohammed, principal of the Fort McMurray Islamic School, said one child remains in hospital.

"This family needs support,” he added. “They need all the prayers that all the people can give."

Mike Allen, the MLA for Fort McMurray-Wood Buffalo, attended the funeral in Edmonton, where two of the four children had been taken to hospital.

“No parent should have to bury their child,” he said, “to see such a tiny little casket.”

RCMP investigators are treating the poisonings as accidental.

Sources have told CTV News that the insecticide used in the apartment was phosphine.

What is phosphine?

Jim Keher, a toxicologist and dean of pharmacy at the University of Alberta, said phosphine is a toxic gas produced when a substance known as aluminum phosphide is exposed to moisture.

Aluminum phosphide is an agricultural pesticide that is tightly regulated in Canada. A special licence is required to use it.

Keher said the children were at increased risk of poisoning because they are closer to the floor.

The pellets scattered in the apartment would have broken down and gotten into the air more quickly after the mother vacuumed the home and disturbed them, he added.

Phosphine may smell like garlic or decaying fish, according to the U.S. Centers for Disease Control and Prevention. However, “the level at which humans detect the odour does not provide sufficient warning of dangerous concentrations.”

The CDC says phosphine poisoning can lead to cardiovascular complications causing death within 12 hours of exposure, and that deaths occurring more than 24 hours after exposure are usually the result of kidney or liver failure.

With a report from CTV’s Alberta Bureau Chief Janet Dirks, CTV Edmonton and files from The Canadian Press