UPDATE: Traffic has begun moving on the Toowoomba Range after earlier coming to a halt.
3PM: Traffic heading up the Toowoomba Range has come to a standstill.
Vehicles are backed up along the west-bound lanes of the Warrego Highway, with police saying the cause was a broken-down truck.
A Queensland Police Service spokesman said a truck had broken-down and was partially blocking the right lane, but there was no room for trucks to pass.
"Only cars can get through. A tow-truck is on the way," the spokesman said.
Cameras on the highway appear to show stationary traffic from around half way up the Range.
Motorist Narelle Schultz said she had been stuck in traffic for the last half an hour.
"My car says 39 degrees. I've probably been here close to a half hour, and I've got from Withcott to not even the saddle," she said.