Illinois State Police says the truck crashed through a wall and landed on newly repaired tracks.
No one was hurt.
The CTA says Red Line trains between 69th and 79th are sharing a single track because of debris on the tracks next to it.
There will be delays, but it is unclear how long they'll last.
Three southbound lanes were closed while crews remove debris late Sunday.
Check back with ABC7 News beginning at 4 a.m. and ABC7Chicago.com for updates on this developing story.