Investigators with Occupational Health and Safety are investigating after two men died on the job Friday.

One 48-year-old man was killed on the Steinhauer Bridge in Fort McMurray when the cab of the semi-trailer he was driving was crushed by the load from another semi-trailer, said OHS spokesperson Jennifer Dagsvik .

A second man, 25, died near Highvale west of Edmonton when he was struck by part of a hoisting assembly from a service rig.

"From the information we’re receiving, he was killed instantly. These blocks came down from quite a distance," said Dagsvik.

Stop work orders have been issued for both sites.