Smoke from an earlier explosion rose from the intersection of Jackson Boulevard and Lasalle mid-day, and "Transformers" cars and trucks rolled down LaSalle near Monroe for several takes. Optimus Prime's red-and-blue semi-truck drew cheers from the crowd excited to see a preview of the film franchise about robots from space that wreak havoc on Earth.
Production assistants said no stars were in town, as stuntmen were performing in the scenes involving helicopters, car stunts, special effects and pyrotechnics.
Mark Wahlberg and Kelsey Grammar star in the Michael Bay film, which is expected to bring $27 million to the local economy, city officials said earlier this year.
LaSalle was scheduled to be closed from Jackson Boulevard to Lake Street from 7 a.m. to 10 p.m. Saturday.