Doctors who treated Pavarotti said that he would have to stay in hospital for a few more days.
A statement from the hospital said several "basic pathological tests" would be carried out, the BBC reported.
The tests "may continue for several more days", the statement added.
It, however, did not divulge any further information about Pavarotti, who is being treated in the cancer ward.
Media reports claimed in recent days that doctors had given a clean bill of health to Pavarotti.
Even a spokesman for Pavarotti recently said that the singer could "be released in the next few days".
The 71-year-old star had been out of public glare ever since he had surgery to remove a tumour from his pancreas last July.