Officers responded to reports of a man running around in the street, appearing to be in distress, in Eleanor Cross Road, Waltham Cross, at about 22:40 BST on Friday, Hertfordshire Police said.

He died in the early hours of Saturday.

The force said it had referred itself to the Independent Office for Police Conduct (IOPC).

The watchdog said it understood officers attempted to stop the man and used pava spray, an incapacitant, as they tried to restrain him.

It said the officers reported the man appeared to be having a mental health crisis so the ambulance service was also called.

The man is understood to have become unwell while being restrained at the scene, the IOPC added.

Officers began CPR until paramedics arrived shortly before midnight, but the man was pronounced dead at 00:17.

IOPC regional director Graham Beesley said: "Our thoughts are with the man's family and friends, and all those affected by this tragic incident.

"Our investigators have begun reviewing body-worn video footage obtained from all officers who attended the incident and will be undertaking door-to-door inquiries in the area."

He said the IOPC inquiry was in its "infancy", adding it was important to carry out a thorough independent investigation to understand the full circumstances.