Victims of possible historic sex abuse against adolescents at a hospital are being urged to come forward.

Hertfordshire Constabulary is investigating reports from a number of sources of physical and sexual abuse against patients at the Hill End Hospital Adolescent Unit between 1969 and 1995, when the unit closed.

The force have launched a criminal investigation, Operation Meadow.

At this stage the number of victims is unclear.

Assistant Chief Constable Bill Jephson said he wanted to "lift the lid" on what may have happened at the hospital.

He urged anyone with information to come forward.

He said: "Hertfordshire Constabulary takes all reports of child abuse seriously, no matter how long ago the offence may have occurred.

"We have officers who are specially trained to deal with these type of crimes while supporting victims in a sensitive, empathetic and caring manner."

The police have launched web pages dedicated to Operation Meadow and are working with other agencies to support victims.

A central email address has also been set up at opmeadow@herts.pnn.police.uk for referrals and will be monitored seven days a week.

No arrests have been made.

The hospital, in the Highfield Park area of St Albans, took patients from the London and Hertfordshire area. It was closed in 1995 and is now the site of a housing development.

Asst Chief Const Jephson added: "Those who believe they have been a victim of this type of abuse are encouraged to make contact with police by calling 101, using our online reporting option through the Op Meadow web pages, or anonymously via Crimestoppers on 0800 555 111 or through their Anonymous Online Form at www.crimestoppers-uk.org."