Four people have been killed and two others seriously injured in a fiery, multi-vehicle collision on Highway 401 near Kingston, Ont.

The crash happened west of Joyceville Road around 1:25 a.m. Thursday.

The Ontario Provincial Police say seven vehicles were involved including four tractor trailers, a commercial truck and two passenger vehicles.

One of the cars became fully engulfed in flames. Police say all four occupants in that vehicle were killed. Their names have not been released.

The investigating is ongoing and Highway 401 westbound will remain closed at Joyceville Road for “an undetermined amount of time.” Detours have been put in place.