A retired headmistress who collapsed and died after burglars posing as water board officials ransacked her home is thought to have suffered a stroke.

West Midlands Police said the death of 90-year-old Hester Mottershead, who was taken ill minutes after witnessing the "despicable" burglary in Tettenhall, Wolverhampton, was being treated as a murder inquiry.

Ms Mottershead, who lived alone, died in hospital on Saturday, having collapsed shortly after three offenders left her home on Friday afternoon.

The pensioner is known to have telephoned police at 2.32pm to give officers descriptions of the men and an account of what happened despite her distress at the offence. Although police arrived within minutes, Ms Mottershead became unwell and was taken to hospital after being treated at the scene by ambulance crews and a doctor who lives nearby.

Speaking outside Ms Mottershead's substantial detached property, named Lawnside, Superintendent Mark Payne said one of the offenders had claimed to be a water official to trick his way into the house.

The officer told reporters: "Our understanding is that a male knocked on the front door of a 90-year-old lady's house. He spoke to her about inspecting some pipes and when she has opened the door another two males have pushed past into the house. They then proceeded for about half an hour to search (the house) and they then left.

"Hester Mottershead then rang the police, but unfortunately when we arrived she was in some difficulty. The officers tried to help her and called an ambulance. Unfortunately, she was taken to hospital and she passed away of what is believed to be a stroke."

Supt Payne said the offenders, who were dressed in blue work overalls or boiler suits, would have been distinctive and would have been noticed by local people.

Urging those responsible for the death to give themselves up, the officer added: "This is a tragic series of events and a terrible way for a 90-year-old lady to end her life. She was extremely distressed. She was a 90-year-old lady and there are very few circumstances that could be any more distressing than having three people in your house searching while you are in there."

Officers have yet to establish what, if any, property was taken by the offenders.