The nurses' union yesterday said it was "unacceptable" that its members were locked-up while they were being questioned by police over allegations of abuse at Mount Carmel Hospital.

A number of Mount Carmel staff members were questioned in recent days, though police have denied any improper treatment.

Sources said police were focusing on one suspect although the possibility of others being involved was not being ruled out.

The allegations against staff involve beatings, extra punishment and degrading treatment of patients with mental health problems recovering at the Attard hospital's juvenile ward, the sources said. The abuse is alleged to have taken place over a period of years.

Contacted yesterday, Malta Union of Midwives and Nurses president Paul Pace said the Union was encouraging members to make an official report to the police to complain about their treatment.

Last week, Mr Pace had complained that two nurses were left in a cell at the police headquarters for some hours, and he said one was strip-searched.

However, police have insisted that no one was maltreated and explained that detaining people under arrest for further questioning was not out of the ordinary when probing a serious case. Mr Pace said there have been several investigations in the past and in none of the cases was a nurse locked up.

"We will be monitoring the situation and will not accept that nurses who are being interrogated to be thrown in a cell," he said.

The union president said the hospital management had offered psychological help to members who had been negatively affected by the incident.