WASHINGTON – An inquiry is underway after nine US hospital patients died, and 10 others fell ill, having being fed intravenously with apparently contaminated liquid food, a spokeswoman said Wednesday.

The 19 people were patients at six Alabama hospitals, and health authorities in the southern state have called on the Centers for Disease Control and Prevention (CDC) to probe the outbreak.

"CDC's investigation is still underway," Alabama spokeswoman Mary McIntyre told AFP, confirming nine of the 19 sickened patients had died.

It was not yet clear whether liquid food was the cause of the outbreak of the bacteria known as serratia marcescens bacteria, but health authorities said all those sickened were patients being fed intravenously.

"Use of contaminated products may lead to bacterial infection of the blood," the Alabama Department of Public Health said in a statement.

CDC has found that the liquid food was supplied by a single pharmacy, Meds IV, which has stopped production and withdrawn the product from sale.