Bangkok  - Lab tests conducted on a 42-year-old Thai woman who was quarantined after showing swine-flu-like symptoms have shown her free of the virus, hospital officials said Wednesday.

The woman, who had attended a seminar in Mexico from April 3 to 11, was admitted to hospital and put under quarantine Tuesday with a light fever, was found to be suffering from ordinary human flu, Chulalongkorn Hospital virus expert Dr Yong Phoosuwan told a press conference.

Like other Asian countries, Thailand has been swift to respond to the swine flu scare.

The government Monday had thermal scanners and quarantine stations set up at its three main international airports to prevent swine flu sufferers from spreading the virus to the population.

There are no direct flights between Mexico and Thailand.

On Tuesday the Public Health Ministry issued an advisory for Thais to avoid travelling to Mexico or the US if possible.

To date there have been no cases of swine flu in Thailand, where the tourism sector was hard hit by the severe acute respiratory syndrome (SARS) scare of 2003 and the avian influenza pandemic of 2004-05.

The Public Health Ministry has put 17 government hospitals on full flu alert and stockpiled of Tamiflu anti-viral medication to treat 300,000 patients.

The World Health Organization has upgraded the pandemic alert level to phase 4, following a swine flu outbreak in Mexico which may have caused as many as 159 deaths, although the exact numbers are questionable.

Mexican authorities have corrected the number of people killed by swine flu from previously 20 to seven.

Miguel Angel Lezana, director of the national epidemiological and disease control centre, said late Tuesday the mutated H1N1 swine flu virus was confirmed to be responsible for seven deaths. The other 13 cases could not be confirmed yet.

Mexican authorities previously put the swine flu death toll at 20. Lezana said additional testing was conducted on recommendation of the the Geneva-based World Health Organization. (dpa)