Bay of Plenty Police are investigating a fatal crash which saw State Highway 5 closed overnight.

Fairfaix is reporting a child was hit by a car on SH5, south east of Tirau, between SH1 and SH28, around 4.51pm.

Police are investigating a fatal crash which closed State Highway 5 overnight. Photo: Christel Yardley.

A St John Paramedic spokesperson says they were called to the crash at 4.48pm and were on the scene at 4.59pm.

He says by the time paramedics arrived, the child had died.

The scene is a rural highway and diversion were in place, but police warned motorists to avoid the SH5 link to allow for a serious crash unit investigation to be completed.

The highway re-opened around 8.30pm.

'No further information will be made until the examination has been completed and next-of-kin notifications have been carried out,” says a statement from police.

People who witnessed the crash, and have not already spoken with police, are asked to contact their nearest police station with relevant information.

Alternatively, information can be left anonymously via the Crimestoppers 0800 555 111 line.