(CBS) -- Police have arrested two people after a robbery attempt in an unusual place -- beneath the streets of Chicago.

WBBM's Bob Roberts reports.

The pair allegedly knocked the woman down around 11:15 a.m. in the pedway beneath the Cultural Center, grabbed her purse and bounded up the stairway at the Millennium Park train station.

A security guard was in hot pursuit and yelled at passersby to help detain the suspects. Two security guards and an off-duty police officer caught up with them, and held them for police.

Police say the victim identified the pair.

Charges were pending.

The Pedway is a series of tunnels beneath downtown Chicago that links transit sites, buildings and retail stores.