A police force is under investigation after two people died in a collision on the M25 motorway involving a vehicle which had been tracked by officers three times before the incident.

The involvement of Hertfordshire Constabulary officers in the crash in the early hours of Sunday morning will be probed by the Independent Office for Police Conduct (IOPC).

A Citroen Dispatch van which had been reported stolen was spotted by officers from the force on the M1 at around 3.40am, the IPOC said.

The officers initiated a pursuit after failing to stop the driver with lights and sirens, but it was abandoned shortly after with the risk of continuing deemed too high.

A second pursuit of the van was made shortly before 4am on Breakspear Way in Hemel Hempstead, but was also abandoned.

The vehicle was then seen by an officer as it was travelling on the wrong side of the M25.

The officer followed the van on the correct side of the road but did not activate their lights or sirens, the IOPC said.

A collision between the van and other vehicles then occurred between junctions 21a and 22 on the motorway at around 4.08am, resulting in the deaths of two people.

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

Essex Police has launched a criminal investigation into the crash.

The IOPC said it was gathering and reviewing evidence to piece together the incident, including police dashcam footage and officers’ body-worn video footage, motorway CCTV and police call logs and radio transmissions.

IOPC regional director Charmaine Arbouin said: “Our thoughts are with all those affected by this tragic incident. 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.”