Passenger Jennifer Chapman of Forest Grove said the female driver of the No. 57 TriMet bus, which serves Hillsboro, forced her and her baby off the bus Thursday night when she couldn't get the child to stop crying, The (Portland) Oregonian reported Monday.
Chapman said other passengers were outraged at the woman's treatment.
"Every single person got off the bus, and it was a full bus, with just two empty seats," Chapman said.
TriMet spokeswoman Mary Fetsch said Sunday complaints were filed by passengers and officials are investigating.
"Obviously, this is something we take quite seriously," Fetsch said.