Ornge Air Ambulance says one person has critical injuries after a serious crash in the area of Fischer Hallman Road and Victoria Street South in Kitchener.
Waterloo regional police said it happened at around 4:15 on Monday.
According to Ornge, a woman in her 20s was transported to a Hamilton hospital with critical injuries. It is unclear if anyone else suffered any injuries.
People can expect heavy traffic and delays in the area due to the crash. Police are asking drivers to find alternative routes.
Just after 5:30 p.m., police said officers will be flying a Remotely Piloted Vehicle (RPV) in the area to collect evidence.