PORTLAND, Ore. -- A loose screw prevented the driver of a streetcar from braking May 24, leading to a collision with two other vehicles in Southeast Portland.

"A screw in the assembly of the streetcar’s master controller — which allows the operator to control the streetcar’s speed — came loose and lodged in the handle mechanism, preventing the operator from stopping the vehicle," Portland Streetcar said in a prepared statement.

Photos: Portland Streetcar crash closes SE Grand Avenue

The crash at Southeast Grand Avenue and Taylor Street derailed the streetcar. One person went to the hospital.

Portland Streetcar said changes have been made in inspection methods to prevent another such incident. The maker of the mechanism has also been asked for guidance.

This was a preliminary finding. The crash remains under investigation by TriMet and the Oregon Department of Transportation Rail and Public Transit Division.

Watch: Time lapse of Portland Streetcar after crash