Center for Disease Control (CDC) deputy director Shih Wen-yi said 13 Taiwanese who had sat near the 44-year-old researcher on a flight from Singapore had been told to monitor themselves closely for signs of fever.

But five foreigners also occupying seats near the SARS-positive patient -- three US nationals, one Japanese and one Singaporean -- had so far not been contacted, Shih said.

"The whereabouts of the five foreigners is difficult to find," Shih said. "We are trying our best to track them down," he added.

The 13 Taiwanese included five colleagues of the victim who had joined him at a medical seminar in Singapore from December 7-10. Two of the colleagues had immediately flown to the United States afterwards but were to return Friday.

All 18 passengers had been on board China Airlines flight CI-662 from Singapore to Taipei on December 10.

Taiwan on Wednesday confirmed its first case of Severe Acute Respiratory Syndrome (SARS) in five months, sparking alarm across the region.

SARS sparked a worldwide health crisis after emerging in China's southern Guangdong province in November last year, causing 774 deaths and more than 8,000 infections, the vast majority in Asia.

The outbreak devastated Asian economies, with the travel and tourism sectors losing hundreds of millions of dollars.

The latest case involved a military laboratory worker who became infected with the killer disease during an experiment at the Institute of Preventive Medicine of the National Defense Medical Center on December 5.

The infection was blamed on lax safety procedures at the laboratory.

The patient was reported to be in a stable condition at Taipei's Municipal Hoping Hospital on Thursday. All people working at the military research complex were also urged to watch for fever, Shih added.

Defense minister Tang Yao-ming Thursday apologized for the negligence of the researcher, admitting there was room for improvement in military laboratory operations.

"He was a very dutiful and careful person ... but it is only human to overlook something sometimes... we will work to improve in the future. I hereby apologise to our people over this case," Tang told reporters.

In one of the most probable causes leading to his infection, the victim did not wear a glove when picking up a contaminated instrument which dropped out of an autoclave during a disinfection process, health officials said.

Various preventive measures had been launched to guard against the resurgence of the disease which had left 37 dead in Taiwan before the island was declared SARS-free by the World Health Organization on July 5.

Shih said all passengers on both domestic and international flights would be screened for fever -- an early symptom of the disease -- before they are allowed to board.

The same requirement also applied to passengers travelling on long-distance buses that take more than one hour, he said. Temperature checks were already carried out since Wednesday at most public buildings.

Seventy people in Singapore were quarantined on Wednesday after coming in contact with the infected researcher during his stay in the city state.

TERRA.WIRE