An 18-year-old man has been arrested in connection with the murder of a nurse in the grounds of the hospital where she worked, police said today.

The arrest followed the discovery of a blue bag in a road close to St George's Hospital in Hornchurch, Essex, where Cheryl Moss was killed in what police described as a "frenzied" knife attack yesterday morning.

Police said the teenager, who was arrested at around 11am, was being held at a north London police station.

Detective Superintendent Dick Langley said the contents of the blue Nike sports bag, found near the river in Upper Rainham Road, had led to the man's arrest.

A source described the arrest as "significant". The 18-year-old, who is believed to live in the local area, is not thought to be related to Ms Moss. It is unclear at this stage whether he knew her.

Earlier, detectives said they did not think it likely that the murder was carried out by one of the hospital patients, most of whom are elderly. Instead, they suspect a random attack by a stranger.

It is the second arrest in connection with the 33-year-old nurse's death. A man detained yesterday is believed to have been released without charge.

Ms Moss, who was married with no children, was repeatedly stabbed as she took a cigarette break in a park area at the rear of the hospital site, which adjoins Hornchurch country park.

She was found by a woman walking her dog just after 11am, and was pronounced dead at the scene despite attempts by paramedics to save her.