Michel Demers demonstrates how he used a hammer to smash the window of the car to rescue the trapped toddler. (CBC)

Police in Laval, Que., are investigating a woman's claim that a 911 operator refused to send police to help get her baby out of a locked car in the extreme heat.

The mother accidentally locked her keys and her 15-month-old son in her car after picking him up from daycare Monday afternoon.

The woman was worried about the potential effects of the scorching heat on her son's health.

Environment Canada had issued a high heat and humidity warning for the region, where temperatures were above 30 C.

The woman ran back to the daycare seeking help.

"The baby was so hot and his face was so red," said daycare owner Josée Lefebvre.

Lefebvre said she called 911, but the operator declined to send assistance.

"I said 'it's an emergency,' and he said 'it's not an emergency, you have to take care of yourself,'" said Lefebvre.

In desperation, Lefebvre's husband, Michel Demers, used a hammer to break the car's rear window to rescue the boy.

In all, the toddler was trapped in the car for about 10 minutes.

Laval police were at a loss to explain the incident.

"I don't have all the details," said Const. Franco Di Genova. "But I do want to stress that this is a type of call that police do go to and respond to."

Officials will be listening to audiotape of the call to determine whether somebody may have misinterpreted the request for help, Di Genova said.