Sydney  - Two Australians recently returned from a trip to Mexico are in a Queensland hospital with symptoms similar to the deadly swine flu, officials said Monday.

"We do have two cases overnight of people checking into hospital whose symptoms are being tested," Queensland Premier Anna Bligh told reporters in Brisbane. "Clearly, this is a very serious disease, and we are taking it very seriously."

In Sydney, two people checked into hospital to have flu-like symptoms checked after returning from Mexico.

New South Wales chief health officer Kerry Chant said that their symptoms were mild and are not consistent with influenza. "There have been some tests performed, but no cases meet the probable case definition, and there have been no confirmed cases," she said.

At least 20 people are confirmed to have died in Mexico from swine flu and more than 60 others have died from what is suspected to be the same viral disease.

The flu has spread to the United States, where 20 cases have been confirmed but no deaths reported, as well New Zealand.

Ten college students tested positive for influenza after their return to Auckland on Saturday, and samples have been sent to a World Health Organization (WHO) laboratory in Melbourne, Australia, for confirmation that they have H1N1 swine influenza.

New Zealand officials said it was "highly likely" that they do, and their families were told to stay in their homes in quarantine until further notice. None was reported to be seriously ill, and all were recovering. Health officials were trying to trace more than 300 other passengers on the overnight flight from Los Angeles carrying the students.

The WHO has declared the outbreak a "public health emergency of international concern," a legal step that put countries around the world on alert. (dpa)