Beijing ? China said Saturday it had sealed off a SARS research lab in its capital after two lab workers contracted the disease and the mother of one died — the world’s first such death this year.

A nurse who looked after one of the SARS-infected lab workers is suspected to have caught SARS and is also in isolation, officials said.

A virus control institute, part of China’s Centers for Disease Control was ordered sealed off, which means people cannot go in or out, state media reported.

“Yes, it has been sealed off,” said a woman at China’s SARS hot line who refused to give her name. Calls to the disease control center rang unanswered.

Last year’s SARS outbreak triggered a global health crisis, killing 774 people around the world and injecting more than 8,000. China reported 349 deaths, the last one in July — before the latest cases.

SARS, or severe acute respiratory syndrome, first emerged in southern China in November 2002.

China today is screening thousands of travelers for fevers at airports and train stations in a massive effort to block a new outbreak of SARS. Hundreds of people with possible exposure to the SARS virus were being held under medical observation.

The government on Friday confirmed that two laboratory employees had the disease and listed a nurse as a suspected case.

The lab workers were identified as a 31-year-old man from Beijing and a 26-year-old woman from central Anhui province — both employees of China’s Centers for Disease Control in Beijing. The 20-year-old nurse works in a Beijing hospital.

The fatality was the mother of the woman from Anhui, and was believed to have caught the virus from her daughter, the government said. The daughter was treated last month at a Beijing hospital, where she came into contact with the nurse.

“When the daughter was ill, the mother accompanied her all the time,” Health Ministry said on its Web site.