A bus fire shut down the ramp from the Mass. Pike to I-495 north in Hopkinton on Monday.Images of bus fire State police said no passengers were on the bus at the time and the driver got out safely.Watch videoWitnesses said they saw smoke coming from the rear engine area before it ignited.The ramp to I-495 was closed for several hours and drivers wanting I-495 north from the Mass. Pike had to take I-495 South to the Main Street/Hopkinton exit to turn around.The luxury motor coach is valued at more than $500,000, the company owner said. The cause of the fire is under investigation.