Two people have died after an outbreak of the MRSA "superbug" at Edinburgh Royal Infirmary, it has emerged.

Both had contracted the bug but this is not thought to have been the cause of death, said a spokeswoman for Lothian University Hospitals NHS Trust.

The patients had been in the hospital's cardiac surgery unit.

The trust was wanted to reassure the public that although inquiries were ongoing, preliminary results had ruled out a single source of the infection, she added.

All heart surgery at the hospital has been suspended since the outbreak began on 6 April.

Resists treatment

There have been no new cases of MRSA, or methicillin-resistant staphylococcus aureus, since the outbreak.

Several patients who remain in isolation are said to be improving.

MRSA can cause infections of the bone and the heart and is referred to as a "superbug" because it resists treatment with commonly used antibiotics.

The infection can cause fever and pneumonia in frail and elderly patients and is primarily transmitted by contact, with poor hospital hygiene blamed in many cases.