The government has launched an internal investigation after a 12-minute power failure occurred at Mater Dei Hospital yesterday morning.

No operations were cancelled and life-saving equipment continued to operate even though the generators did not kick in automatically.

However, there were four reports of people stuck in lifts who were let out after 10 minutes, a spokesman for the Health Parliamentary Secretariat told The Times.

The power cut, which started at 10.35 a.m., was the result of problems in the hospital's power network control centre, the government said in a statement, as it highlighted that hospital operations carried on normally.

Asked why the generator had failed to kick in, the spokesman said the automatic mechanism only functioned when the power cut was due to a failure from Enemalta's side. Since yesterday's power cut was caused by an internal problem, and not due to Enemalta, the generator had to be switched on manually.

Asked whether there were plans to change this system since, as yesterday's incident showed, power cuts were not always caused by an Enemalta failure, the spokesman said this was a technical issue that would be dealt with after seeking the necessary advice, as part of the internal investigation.

He explained that vital life-saving equipment, including that in surgical theatres and the Intensive Therapy Unit, operated on uninterrupted power supply and continued functioning normally without any interruption.

The uninterrupted power supply operates on batteries and does not need to be switched on after a power cut.

It is understood that most life-saving equipment can also be operated manually if necessary.

According to the spokesman, operating theatres are not thrown into darkness during an electricity cut.

He explained that the operating table light, which is used by the surgeon to light the table, operated on an uninterrupted power supply while a number of other lights had a battery backup which would run until the emergency lights switched on or the electricity supply was restored.

A number of electricity outlets also operated on an uninterrupted power supply to ensure that life-saving equipment continued functioning.

The multimillion euro hospital was inaugurated in June 2007 and received its first patients in November of that year, after years of controversy and changes to plans.