Darlene Ferguson, 51, died in an explosion at a resort hotel in Playa del Carmen, Mexico, on Sunday. (Courtesy Edmonton Journal)The ambulance that transported Alberta explosion victim Darlene Ferguson to hospital in Mexico on Sunday ran out of gas along the way, family members told CBC News Friday.

Ferguson, 51, was one of seven people, including five Canadians, who were killed Sunday in the explosion at the Grand Riviera Princess resort in Playa del Carmen.

Ferguson, a mother of three who was in Mexico for her son's wedding, was taken to hospital in Cancun for treatment after the blast, where she died.

When the ambulance ran out of gas, attendants asked Ferguson's daughter Katie to pay for the gas, her brother Barry Hoffman said.

"It's just terrible, actually," he said.

Hoffman said his sister was taken to three different medical facilities.

"All in all, it took three hours before she got actual treatment," Hoffman said. "Three hours is just an unreasonable amount of time."

Katie Ferguson, who is a registered nurse, noticed that the ambulance attendants had placed the respirator on her mother incorrectly.

Mexican authorities announced Thursday that they have opened a homicide investigation into the explosion.