A woman of 90 sparked a police hunt after making an emergency call to say she was trapped in a strange house.

Officers and hundreds of members of the public were put on standby for nine hours as high-level clearance was given to trace the phone from which the distress call was made.

Detectives feared they might have to scour dozens of homes along Brighton Road between Shoreham and Worthing as this was the only detail the woman had given in her frightened message left on a social services answering machine.

She said she had gone into a house to investigate a broken window but the door had closed behind her, locking her in.

West Sussex social services alerted Adur police at Shoreham and a major operation was launched.

Sergeant Ian Cooke said: "All we had to go on was this house was near a parade of shops on the Brighton Road.

"It's a huge area to search and we had no proper indication of where the call had come from or why it had been made to social services rather than the police.

"Without a proper location we had nowhere to focus a house-to-house search so we had to try to trace her by other means.

"We contacted the ambulance service and other agencies to see if they had records of any women in their 90s who had missed an appointment.

"Social services and the Women's Royal Voluntary Service's meals-on-wheels drivers were asked to check none of the clients they were due to see were missing.

"We got permission at Assistant Chief Constable level to try to trace the phone from which the call had been made.

"This can take hours because it is such a complex procedure so, in the meantime, we put hundreds of neighbourhood search team volunteers on standby to look for her."

But the hunt was called off after nine hours when the telephone trace revealed the call had been made from an elderly people's home in Durrington Lane, Worthing.

Mr Cooke said: "It has a number of residents with dementia which can cause them to become confused and unsure of their surroundings. The staff knew nothing about the call but confirmed none of their residents was missing.

"We still don't know who made the call but we had no choice other than to respond in the way we did.

"For all we knew she may have been trapped in a building where the owners were away on holiday."