Chopper 7 was over the scene at about 6:45 a.m. on northbound I-57 at 159th Street.
By 7 a.m. it appeared that firefighters had the blaze under control.
It was not clear what started the fire.
Illinois State Police said the fire started at about 5:48 a.m. and no injuries were reported.
The company debuted the "Maxxinista Express" over the holidays.
The bus was heading to Chicago on Wednesday to begin Mother's Day celebrations.
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