Investigators say a passenger got on the bus on Alexander Drive near East Cornwallis Road and saw a clear bag in between seats that was marked "biohazard."
The passenger told the driver who called authorities.
The passenger and the driver were the only two people on the bus at the time. Both were checked out by paramedics and found to be okay.
A hazardous materials team removed the bag from the bus and analyzed it to see what was inside.
Traffic on Alexander drive was down to one lane as emergency workers did their job.
After testing, it was determined that the bag contained water.
Investigators are now trying to find out where it came from.