A major investigation is underway after a five-vehicle crash on Highway 7 sent six people to hospital on Sunday evening. Lanark OPP responded to the collision in Innisville around 5:30 p.m., where they found victims ranging in age from 17 to 78.

Three people suffered injuries that were considered potentially life-threatening, including a senior who remained in the most serious condition. The remaining three individuals were treated and expected to be released Monday.

Police say the crash occurred during fair weather, though visibility was reduced by some dusk fog. According to investigators, the chain reaction began when a vehicle slowed to turn into the Ultramar gas station.

Highway 7 was closed until 4 a.m. Monday while officers examined the scene. OPP are urging drivers to respect the reduced speed limits in the area and to slow down when entering or exiting the roadway.

Anyone who saw the collision or has relevant dash cam footage is asked to contact Lanark County OPP and reference incident E251583748.