AUBURN — A faulty valve on two empty tanker cars appears to be the cause of a small leak of residual chlorine on the rail lines along Black Cat Road early Monday afternoon, authorities said.

The valve was repaired and the leak was contained, police said at about 5:30 p.m.

Emergency response crews that had donned special protective suits to address the problem began the decontamination process Monday evening.

Police blocked the intersection of Washington Street and Station Road and the intersection of Black Cat Road and Old Danville Road, and set up a command post at Crossroads Market on the west side of Washington Street near Exit 75 of the Maine Turnpike. All roads are expected to be reopened by 6:30 p.m., police said.

The leaking cars were believed to be about 1,000 feet south of the intersection of Black Cat Road and Station Road.

Maine Department of Transportation spokesman Ted Talbot said the initial call came in at 12:05 p.m., when employees on the Pan Am line detected the chlorine smell.

According to Auburn Deputy Chief Jason Moen, there had been no immediate risk to the community. A nearby homeowner was asked to remain inside their house, but local businesses remained open, as did the Maine Turnpike entrance on Washington Street. Police lifted that order at 6 p.m.

Local school buses were rerouted.

Auburn police and fire officials, as well as railroad officials, were at the scene.

According to Talbot, the Federal Railroad Administration will be taking the lead on any investigation.