According to officials, the collision between two cars took place in the area of 488 Main Street.
An area of Route 6 was closed for a period of time between Harwinton Avenue and Seymour Road. Police diverted traffic around the accident scene.
According to the Plymouth Police Department, both drivers had to be extricated from their vehicles.
Officials say there a total of four victims. One person was flown via Life Star for treatment. The three others were all transported to local hospitals. There is no word on the status of their conditions.
WEB Extra: Video captures the scene of a serious multi-vehicle crash in Plymouth (Video Credit: AM News Network)
News 8 will update this story with more information as it becomes available.