Flames engulfed a Ramblin Express tour bus en route to Cripple Creek from Pueblo, stopping traffic Sunday morning on northbound Interstate 25 about 16 miles north of Pueblo.

The bus driver first reported a tire fire, according to the Colorado State Patrol.

The driver ushered about 25 passengers off the bus and tried to put the fire out himself before realizing he couldn't, said Ram- blin Express General Manager Gary Agnes.

By the time firefighters arrived, more of the bus was burning. It then became fully engulfed.

Firefighters also were working what may be a related grass fire along I-25, 10 miles from the bus.

"We have no idea how the fire started," Agnes said. "We are just thankful no one was injured."