(CNN) -- A shuttle bus crashed Friday morning at Chicago's O'Hare International Airport, injuring 15 people, police said, and temporarily snarling vehicle traffic at one of the world's busiest centers for air travel.
The bus, shuttling people between the terminals and a rental car company, was leaving Interstate 190 on a lane toward a terminal when it struck a concrete median about 6:30 a.m. CT, CNN affiliate WBBM reported.
Fifteen people were injured and were being taken to hospitals, but the severity of their injuries wasn't immediately clear, Chicago police spokeswoman Ana Pacheco said.
The injured included the driver, who for a time was pinned by a guardrail that penetrated the bus upon impact, CNN affiliate WLS reported. Two Chicago firefighters who witnessed the crash freed the driver and then helped other passengers, WLS reported.
Details about what caused the wreck were not immediately available.
The wreck prompted the closure of some I-190 lanes and caused traffic backups on the interstate on Friday morning, WLS reported.