UPDATED 10/07/11 1:35 p.m.

FOREST PARK, Ill. (CBS) — The Forest Park branch of the Blue Line was shut down along its westernmost stretch Friday morning, for a report of a suspicious package that turned out to be a false alarm.

The Chicago Transit Authority received notice about an unattended package, and as of the 10 a.m. hour, the Blue Line was halted between the Forest Park terminal and the Harlem stop as police investigated at the scene.

A shuttle bus was put in place in lieu of the trains, police said.

By about 11:15 a.m., Forest Park Deputy Chief Tom Aftanas said the package had been “deemed a false alarm,” and service soon returned back to normal.

Aftanas told the Sun-Times Media Wire that police detonated a water-based explosive to open the package, which looked like a tackle box. It turned out to contain harmless, miscellaneous electronic parts, Aftanas told the wire.

Someone likely left the box on the train by accident, Aftanas told the Sun-Times Media Wire.