CHICAGO (CBS) — The cold weather has created an unpleasant trend on the CTA’s Red Line.

Human feces.

READ MORE: Chicago Weather: A Few Sprinkles Overnight

A CTA spokesman confirms there have been a “handful” of complaints about people using train cars as a toilet. The incidents are believed to be related to homeless people seeking shelter on trains in the extreme cold weather.

And more cold weather is expected this week.

READ MORE: Video From Police Shooting That Killed Adam Toledo To Be Released On Thursday, COPA Says

Riders have been discovering the human excrement and have been forced to move immediately to other cars.

The CTA inspects trains after each run and cleans up the cars as needed, a CTA spokesman told CBS 2.

CTA security staff and experts from social service agencies are working to encourage homeless people to take advantage of shelters and social services.

MORE NEWS: Five Things We Know About The Adam Toledo Police Shooting Case

The Red Line, along with the Blue Line, operates 24 hours a day.