BEIJING (Reuters) - Chinese health authorities said they are investigating 27 cases of viral pneumonia in the central city of Wuhan, after rumors on social media suggested the outbreak could be linked to Severe Acute Respiratory Syndrome (SARS).

Of the people infected, seven were in critical condition and 18 were in stable condition, the Wuhan Municipal Health Commission said on Tuesday on its Weibo social media account. The condition of two other patients had improved to the point where they would be discharged soon, it said.

“The cause of the disease is not clear,” the official People’s Daily newspaper said on Weibo, citing unnamed hospital officials. “We cannot confirm it is what’s being spread online, that it is SARS virus. Other severe pneumonia is more likely.”

All of the patients had been isolated and their close contacts are under medical observation, the Wuhan Municipal Health Commission said. An investigation and cleanup were under way at a seafood market in the city, which is suspected to be connected with the cases, it said.

Initial laboratory tests showed that the cases were viral pneumonia. No obvious human-to-human transmission had been found and no medical staff had been infected, the commission said.

A team of experts from the National Health Commission is in Wuhan to carry out tests, state broadcaster CCTV said.

An official at Wuhan Central Hospital, where local media said some of the cases are being treated, declined to comment when contacted by Reuters.

In 2003, Chinese officials covered up a SARS outbreak for weeks before a growing death toll and rumors forced the government to reveal the epidemic, apologize and vow full candor in future outbreaks.

The disease, which emerged in southern China in late 2002, spread rapidly from south China to other cities and countries in 2003. More than 8,000 people were infected and 775 died.