Officials say the crash took place around 6:15 p.m. on Route 8 Northbound near exit 42.
The route is closed between the exit 42 ramps while crews work to clear the scene.
According to police, Life Star transported one person to a local hospital for treatment, while another victim was driven to a hospital. Animal control was also called to the scene to transport one dog to an emergency veterinarian.
#CTtraffic: Rte 8 nb between x42 ramps Harwinton closed for rollover crash with life-threatening injury.
— CT State Police (@CT_STATE_POLICE) December 25, 2017
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It is not known how many vehicles were involved in the incident.
The cause of the crash is unknown at this time.
Officials have not said when they expect the road to reopen.
News 8 will update this story with more information as it becomes available.