PEACE RIVER, A.B. – Four people were killed and three seriously injured on roads in the Alberta Peace after four crashes occurred in the span of less than 12 hours – three of which happened less than two hours apart.At 3:43 on Tuesday afternoon, members of the Spirit River RCMP were dispatched to crash on Highway 2 at Township Road 763.A pickup truck travelling west on Township Road 763 collided with an unloaded semi-truck travelling south on Highway 2. Then on Wednesday morning, two more people were killed in a two-vehicle crash that occurred near Peace River.The crash happened just after 1:00 a.m. on Highway 2 near Range Road 252 and involved two SUV’s.The two occupants of one of the SUV’s, a man and a woman, were pronounced dead at the scene.RCMP Corporal Laurel Scott said that the identities of the two deceased have not yet been positively confirmed.Meanwhile, the two female passengers of the other SUV were airlifted to an Edmonton hospital with serious injuries.Highway 2 was closed for over six hours while the RCMP’s collision analyst investigated the scene, and the road reopened shortly before 7:30 this morning.Cpl. Scott added that at this point, it’s not known what caused the collision. At around 5:30, members of the High Prairie RCMP were called out to a single-vehicle rollover collision on Alberta Highway 750 in the community of Grouard, approximately 30 kilometres northeast of High Prairie.Police say that a northbound car crossed the highway’s centre line and went into the ditch on the opposite side of the road before it rolled onto its roof.The lone occupant, a 48-year-old man from McLennan, Alberta was pronounced dead at the scene.The RCMP say that their investigation is ongoing, and are asking anyone who witnessed the crash to contact High Prairie Detachment. The 84-year-old driver of the pickup was airlifted by STARS to an Edmonton hospital in serious condition, while the driver of the semi was unscathed.An hour later, police responded to a two-vehicle collision on Highway 49 and Range Road 110.Police say that according to the preliminary investigation, a tractor-trailer unit travelling westbound on Highway 49 was attempting to pass a tractor, which was hauling hay.At the intersection of Range Road 110, the tractor initiated a left turn, and the two vehicles collided.The 74-year-old male driver of the tractor was declared dead at the scene, while the driver of the semi was uninjured.The Spirit River RCMP saw that both collisions remain under investigation.