The Alberta Serious Incident Response Team, known as ASIRT, said in a news release that the pair was killed Friday near Redcliff, northwest of Medicine Hat.
Medicine Hat police said officers went to a home in the city after a woman in distress called 911.
When they arrived, there was no one there, but police said there were signs that a woman was in danger.
"Evidence found in the residence led police to believe someone had been forcibly confined," said a statement.
About an hour later, police spotted a vehicle linked to the home and leaving the city. Officers followed it for a short distance.
At one point, it's passenger door opened and closed.
"Actions occurring in the vehicle, along with observations from the residence, reinforced the fear that the female passenger was in imminent danger."
Police said they tried to stop the vehicle but it took off, so a chase began. RCMP took over the pursuit when it reached city limits.
ASIRT said the two people in the vehicle died when it collided with a semi truck.
Their names have not been released.
The driver of the truck was taken to hospital with minor injuries.