Workers clean out a closed poultry market in Beijing Monday Nov. 7, 2005

China is investigating three potential cases of human infection with the H5N1 virus, while the EU health commissioner is visiting the region to support Southeast Asia's fight against the bird flu.

The Chinese government said it could not rule out bird flu in the death of a 12-year old girl, and the illnesses of two other people. Beijing invited the World Health Organization to investigate three suspicious cases of pneumonia in the southern province of Hunan, where avian influenza was found among birds last month.

Authorities had earlier denied any connection between the pneumonia cases and the deadly H5N1 virus. But state media said Chinese health officials had decided samples from the girl, her brother, and a schoolteacher needed more analysis.

The World Health Organization says it is not unusual for someone to initially test negative for H5N1, but later test positive. Julie Hall, a doctor with the WHO office in Beijing, says final results on the suspected cases could take weeks.

"That is because the testing that is required is quite complex and it is very important that we have late samples - samples taken a long time after a patient has first developed any symptoms," said Dr. Hall. "Those samples are very important for testing to see if the patient has developed any antibodies."

If confirmed, the cases would be China' first reported human infections with the H5N1 virus.

Because of the size of the country and its overstretched health-care system, there has been concern that bird flu could move quickly into humans in China before it was detected.

There also has been fear among many international disease experts that Chinese officials in rural areas would hide flu outbreaks, much the way the central government tried to hide news about the appearance of SARS in 2003. The disease appeared first in China, but spread around the world before Beijing answered WHO questions about it.

Alarmed by four outbreaks in one month, the country has stepped up its fight against the avian flu. China announced Monday it has killed six million birds in the northeastern province of Liaoning, where the country's latest outbreak had been detected last week. Authorities also ordered the immediate closure of Beijing's 168 live poultry markets.

In Vietnam, the Health Commissioner of the European Union, Markos Kyprianou, met with agricultural and health officials in Vietnam. They discussed how the European Union can help contain the deadly strain of bird flu that has recently spread from Asia to Europe. He said the European Union has pledged to give more than $35 million to Asia to fight avian influenza.

Christoph Wiesner, with the European Commission office in Vietnam, says Brussels does not just want to provide emergency funding.

"One also has to look at the medium-term situation to not just fix the holes if they appear, but to make sure there is a stable and viable framework in the country that can ensure that they can deal with future outbreaks because it is clear that the problem is here to stay," said Mr. Wiesner.

After his three-day visit to Vietnam, Health Commissioner Kyprianou will travel to Thailand, Cambodia, and Indonesia to discuss the measures they are taking to contain the spread of bird flu.