4:54 PM PT -- Reps for the bands tell us ... no one lost any equipment or personal belongings in the fire ... the bands are on a three day break and everyone had taken most of their things off the buses.
Two tour buses for a Styx and Foreigner concert turned into vehicular torches early Wednesday afternoon in Philly ... TMZ has learned.
It's unclear how the fire started, but we're told one bus went up in flames ... and the fire spread to the second vehicle.
The buses were parked and NOT occupied when they caught fire. We're told the buses are "crew buses" and not "band buses."
The bands are scheduled to perform together Thursday in New Jersey.
In case you don't remember Styx -- you should be ashamed of yourself -- they had a bunch of hits including "Babe," "Renegade," "Mr. Roboto" and "Come Sail Away."
As for the concert, the show presumably will go on.