The dead had been travelling in a VW Touran people carrier, when it was hit by a black VW Golf.
the Golf car was being pursued by police.
The victims were two men aged 35 and 50 and a woman aged 41. A one-year-old boy died later in hospital.
Two women are in hospital - one is in a critical condition and the other is serious but stable. A three-year-old girl is also in hospital with life-threatening injuries.
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Three men aged 23, 17 and 18, who had been in the Golf, were injured. They are under arrest.