Police in Mississauga, Toronto and Halton Region are appealing for witnesses after a series of deadly accidents on Friday night and Saturday morning.

Four people died — two of them children — in three separate accidents on GTA highways.

A 13-year-old girl died when she was struck by a 2002 Chevrolet Impala in Mississauga on Friday evening while she was standing on the sidewalk..

Peel Regional police say the accident happened at about 8:30 p.m. near Dixie Road and Bloor Street.

Less than half an hour later, a two-vehicle collision near Highway 50 and Fogal Road in Brampton killed a 40-year-old father and his five-year-old daughter.

The mother, who was driving the Toyota van, was taken to hospital with non-life-threatening injuries but a three-year-old daughter ,who was also in the vehicle, was airlifted to Toronto with life-threatening injuries, according to police.

The 27-year-old male driving the Ford F-350 which "violently collided" with the vehicle carrying the family, suffered non-life-threatening injuries.

And an accident on Highway 407 on Saturday morning killed the driver of a dump truck.

Police say it appears the man lost control of his truck and hit a concrete barrier and then a light pole just east of Bathurst Street.

"It is unknown at this time why the dump truck lost control," said a statement from the OPP.

So far no names have been released.