'iCarly' Star Miranda Cosgrove Tour Bus Accident -- Broken Ankle

"iCarly" star Miranda Cosgrove suffered a broken ankle when her tour bus crashed into a tractor-trailer in Illinois this morning ... her rep tells TMZ.

The rep explains, "Miranda Cosgrove's tour bus was involved in an accident early this morning in Illinois on I-70, just outside of Vandalia."

The rep adds, "There were 5 passengers on the bus, and Miranda suffered a broken ankle. At this time, we are told everyone will be fine."

Cosgrove -- who is also a singer -- had been performing in Ohio on Wednesday night and was traveling to Kansas where she was scheduled to perform on Friday.

Miranda's rep tells us the 18-year-old Nickelodeon star's "Dancing Crazy Tour" will now be postponed until further notice ... adding, "Miranda thanks everyone for their understanding and support."

According to local reports, the tractor-trailer was already overturned and the bus hit a part of the vehicle that was blocking one of the lanes.