Chopper 7 HD flew over the scene near the 147th Street and Sibley Station in Harvey around 5:30 p.m.
Police from Chicago, Harvey and Riverdale are involved.
There were reports officers were looking for suspects in a robbery.
Metra posted the following on its website at 5:46 p.m.:
"The following trains will be delayed in departing University Park and Chicago: #136 to Depart University Park at 5:40pm to arrive Chicago at 6:46pm; and #139 departs Chicago at 6:08pm and arrives University Park at 7:08pm. This is due to earlier police activity 147th. These trains may be delayed up to 50-60 minutes."
Metra Electric Line trains were moving again by about 6 p.m.
