At least eight dogs died from heat stroke and other were rushed to veterinary hospitals when the air conditioning failed in a truck carrying them to an Indiana K-9 training facility Thursday.

The driver of a truck was bringing 18 dogs from O'Hare International Airport to a K-9 training facility in Michigan City, IN, the Lake Station (IN) Police Department reports on Facebook.

Lake Station officers said the temperature began rising after an AC unit in the cargo area stopped working when the vehicle became caught in traffic for two hours, NBC Chicago reports. With the cargo area separated from the driver, he didn't immediately realize what was happening until some of the dogs started barking, police said.

The driver subsequently stopped at a gas station in Lake Station. He entered the cargo area, police said, saw that canines were in distress and began removing those that had been placed in crates. While passersby stopped to help, calls were made to 911, resulting in a response from police, firefighters and EMS personnel. Civilians also tried to help the animals.

Multiple dogs were evacuated by ambulance to a veterinary hospital. Some of them had to euthanized.