Two U.S. tourists—a man and a woman—have gone missing after an avalanche in Banff National Park in the Canadian Rockies. Authorities say the Boston residents’ car was located near a lake inside the park, and the pair failed to check out of their hotel on Tuesday as planned. A search-and-rescue team was sent out to find the snowshoeing tourists, but it was only able to locate their tracks leading to the site of the avalanche before the risk of another avalanche halted the operation. Parks Canada, which is in charge of the search operation, said signals had also been picked up in the area from two radio-distress transmitters. The missing Americans have not been identified, but Canadian authorities say their families were notified of the situation.