International health experts expect to identify the mysterious flu-like disease afflicting parts of Asia within days, though finding a treatment may take more time, a UN health official said today.

"I think we can identify the causative agent in quite a short time period. Probably within a few days, at most a few weeks," said Hitoshi Oshitani, the World Health Organization (WHO) regional coordinator for severe acute respiratory syndrome (SARS).

"But this doesn't mean we will find the specific treatment for this disease within the short time period," he said.

Researchers suspect the disease, described by Mr Oshitani as "the most significant outbreak that has been spread through air travel in history", was caused by the paramyxovirus or the coronavirus.

The paramyxovirus causes measles and pneumonia in children, and the coronavirus is the major cause of the common cold.

Mr Oshitani said the virus causing SARS possibly came from an animal. He ruled out the possibility of a link with bird influenza, which has infected the Hong Kong poultry in recent years.

Mr Oshitani said identification of the cause would help health experts develop a diagnostic test, but they would still be a long way from finding the cure, he said.

The disease has so far infected more than 1,600 people in 15 countries worldwide, and has killed 59 people. China, Hong Kong, Singapore and Vietnam are among the hardest hit countries.

Masked police today quarantined off one apartment block in Hong Kong's Kowloon Bay area after 107 residents came down with the mystery illness. HSBC bank also ordered 50 of its staff in the city headquarters to remain at home for seven days after a teller contracted the disease.

In China, people in the Guangdong province have been rushing to buy surgical masks and herbal cold remedies. Taiwan today began cutting flights to Hong Kong, fearing the spread of the illness to the island.

The WHO has established a collaborative multi-centre research project to find a cure and is coordinating with at least nine laboratories in 11 countries.

Mr Oshitani described SARS as "more highly contagious" than the Ebola virus which struck rural Africa several years ago. The spread is aided by the fact that it has struck highly populated areas.

Symptoms include high fever, dry cough and breathing difficulties.