"Anti-body examinations show the possibility of corona virus infection, but the test results on the antigen are not consistent," the ministry said in its daily SARS report on Wednesday.
"At present our nation's experts are cooperating closely with experts from the World Health Organisation and are testing samples from the infected person in the effort to produce a quick and clear diagnosis."
China decided late on Tuesday to send samples to an outside lab affiliated to the WHO, or possibly more than one, WHO spokesman Roy Wadia said in Beijiing.
"In this case, it's been so confusing because the few positives that have emerged from the battery of tests are from tests that historically have a high number of false positives," Wadia said.
No need for panic
Confirmation of the case should come "within a week", a WHO spokesman said in Geneva, adding that there was no need for panic.
"Because of the sensitivity of saying it is or it isn't SARS both we and the Chinese want to be absolutely certain about what we are dealing with before we start making pronoucements about it," Ian Simpson said at the WHO headquarters in Geneva.
"Because of the sensitivity of saying it is or it isn't SARS both we and the Chinese want to be absolutely certain about what we are dealing with before we start making pronoucements about it"
"We would hope that we would know within a week but it is difficult to put a clear timeframe on it," he said.
"It is very important to know as soon as possible, but it is also very important to be right so it is a question of finding the right labs, sending them the samples, getting the results," Simpson added.
The decision is likely to delay a diagnosis on the 32-year-old television producer in the southern province of Guangdong with symptoms of SARS.
China has quarantined 81 people who have come in contact with the TV producer, and the ministry statement said 23 had been released.
China's cooperation with the WHO on the case is in marked contrast to its response when SARS first emerged more than a year ago.
The WHO and other countries had said China's attempts to initially sweep the problem under the rug probably caused the disease to spread more quickly.
Feng Shaoming, an official at the Guangdong health administration, dismissed reports in which he was quoted on Tuesday as saying the patient had already been confirmed SARS positive.
Three labs in China had run tests on the patient - one under the health ministry, one under the Centre for Disease Control and one belonging to the Guangdong health authorities,
Zhong Nanshan, one of China's top respiratory experts, said some tests showed the patient was infected with SARS.
"Yesterday, in Beijing, we conducted a comprehensive test. The comprehensive test, which included tests on the patient's serum and antibodies, showed the patient was infected with the SARS virus," he said.
"There is not a very obvious origin of infection. If there is a case in the community, we need to be very careful in confirming it. That's a main reason why up to now the case has still not been confirmed."
SARS emerged in Guangdong in late 2002 and travellers spread it to nearly 30 countries.
About 8000 people were infected around the world and about 800 of them died.
About 350 of the deaths were in China out of more than 5000 who became ill with the disease.