Vienna - One Austrian woman was "likely" infected with swine flu and four others are suspected of having the same illness, Austrian Health Minister Alois Stoeger said Tuesday.

All of the five had recently been to Mexico, the centre of the outbreak, the minister said at a press conference.

The most likely case is that of a 28-year-old woman in Vienna, who returned last week from a trip to Guatemala and Mexico, Vienna's chief health official Karin Spacek said.

Initial tests showed the woman to be suffering from an uncommon variety of type-A influenza, increasing her chances of being infected with the H1N1 virus. She also showed symptoms typical for swine flu.

The country's first publicly known case was that of another 28-year-old woman who was admitted to a hospital in the town of Steyr on Tuesday, where she was immediately put in an isolation unit, a hospital spokeswoman told German Press Agency dpa.

A laboratory in Vienna was running additional tests after initial results showed the woman was not infected with the virus.

The other three patients, a 65-year-old tourist and a couple in their 70ies, are all in Vienna.

All of the patients have been hospitalized, and suffer from typical flu symptoms. Definite test results were expected on Wednesday.