Two 10-year-old boys were killed and four other people were injured when a car fleeing a traffic stop crashed in southern Wisconsin, police said.

The Waukesha County Sheriff’s Department said a deputy stopped the car for speeding and driving without license plates just before midnight Wednesday, but the driver sped away with five passengers in the vehicle.

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A police pursuit involving two deputies began in Pewaukee and ended miles away when the car was involved in a rollover crash in Delafield, about 25 miles west of Milwaukee, police said.

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Two 10-year-old boys died in a Delafield, Wisconsin, rollover crash after their father tried to flee from law enforcement.

"The driver fled at such a high rate of speed that my deputies weren’t even in visual contact during the crash," Sheriff Eric Severson said Thursday.

Two 10-year-old boys died in the one-car crash, while two girls, ages 14 and 6, were hospitalized in critical condition, police said. A 29-year-old man who was the car's driver was in critical but stable condition and a 29-year-old woman was in stable condition.

Authorities have not released their names. But the sheriff’s department said both boys were the driver’s sons, the 29-year-old woman is the driver’s girlfriend and the 6-year-old girl is their daughter. The 14-year-old girl is the driver’s niece and all six crash victims are from Milwaukee, police said.

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The pursuit and the resulting crash will be investigated by the Washington County Sheriff’s Department and the Wisconsin State Patrol.