CHICAGO (CBS) — CTA Green and Pink Line service was halted in the West Loop early Tuesday because of an unauthorized man on the tracks.

Police were called about 2:30 a.m. for reports of the man running back and forth on the tracks between Morgan and Carpenter, according to Chicago Police. The CTA has cut power to the tracks and police negotiators were on the scene trying to get the man to come down.

The CTA announced shortly after 4 a.m. that Green Line service was suspended between the Pulaski and Clark/Lake stations. Pink Line trains were only running to Polk and then connecting with the Blue Line at Racine. Shuttle buses are available for affected riders.

(Source: Sun-Times Media Wire © Chicago Sun-Times 2016. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)