M25 crash: Van had been driving against traffic near St Albans

Hertfordshire Police said a police pursuit was stood down twice prior to the collision between the London Colney and St Albans junctions on the M25

The van involved in a collision where two people died had been driving against traffic on a motorway.

The Independent Office for Police Conduct (IOPC) is investigating Sunday's crash on the M25 between junction 22 and 21A near St Albans.

Hertfordshire Police had followed the stolen white Citroen Dispatch from the correct side of the road, but had not activated lights or sirens.

The van driver was taken to hospital and remains in a serious condition.

Police said a woman died in the four-vehicle crash on Sunday, and on Tuesday the force confirmed a man had also died.

A man in his 20s has been arrested on suspicion of causing death by dangerous driving.

The incident was referred to the IOPC for investigation over the "police actions prior" to the crash.

According to investigators the stolen van had been first spotted by officers in a marked car travelling on the M1 at about 03:40 GMT.

A pursuit was initiated but then abandoned because officers assessed that the risk of continuing was too high.

Then a subsequent pursuit took place shortly before 04:00 on Breakspear Way, Hemel Hempstead, but this was also abandoned a few minutes later.

At about 04:08, the van was spotted being driven on the wrong side of the M25 moments before being involved in the collision, police said.

A criminal investigation into the incident is being carried out by Essex Police.

IOPC regional director Charmaine Arbouin said: "Given that police officers were pursuing one of the vehicles before the fatal collision, it's important that we independently investigate the actions and decision-making of the officers involved.

"We will ensure that our inquiries do not impede the police investigation, and we will keep those involved regularly updated."

Police renewed their appeal for witnesses and dashcam footage. The other three vehicles were a silver DFSK 580 Glory, a silver Skoda Superb and a black Peugeot 5008.