Gastro outbreak at The Alfred in Melbourne

The Alfred hospital in Melbourne has been hit by a gastro outbreak with patients falling ill.

An investigation is underway after up to 20 patients suffered "gastro-like symptoms" at the hospital over the weekend, a spokeswoman told AAP on Tuesday.

"Most of those patients are no longer experiencing these symptoms and are doing well. Some patients have been discharged," she said.

The outbreak was concentrated in one ward and an investigation is underway to identify the cause.

Infection prevention measures are continuing as a precaution, the hospital said in a statement.