With millions of people sharing news and views every day through micro blogs, or Weibo, its no surprise that rumors spread so quickly.

That's why people like Tan Chao are there to nip them in the bud.

As director of "rumor control" for micro blog service Sina Weibo, Tan heads a small team that monitors posts and removes anything that turns out to be false.

"The job is vital, as we want to protect the truth and maintain an unpolluted Web," he said in a phone interview on Wednesday.

"There is a lot of information on Weibo, much of it eye-catching, which means it attracts a lot of people. Yet users are not always good at judging what is true and what is false. They can be easily misled."

A case in point is the rumor that circulated on Weibo on Oct 26 that a knife-wielding teacher had taken students hostage at Beijing No 55 Middle School. China Daily was among several media organization that sent reporters to the scene only to find it was completely made up.

"If these things are posted on our service, it's important we catch them and take them down to protect our image as a reliable source," said Tan.

Based at Sina's Beijing headquarters in Zhongguancun, a hub of high-tech activity, the rumor control office consists of 10 people, including Tan, and is staffed 24 hours a day.

Working in eight-hour shifts, members trawl micro blogs and follow up users' complaints about erroneous posts while a duty editor checks and verifies information.

The average age of the team is 28 and most are senior journalists recruited from Sina's media center.

"Having a good news sense was an important factor when we were hiring," said Tan. "The work needs people to be keen-eyed and good communicators.

"In fact, three of the people here now have a lot of experience in traditional media, mainly newspapers or magazines, which saves time in detecting false information and finding facts."

Although some investigations can be as simple as reading a news source, Tan said that at times researchers are forced to call people involved in the post to confirm the facts.

Aside from manpower, Tan said the company also uses a computer system to search for rumors. However, he refused to elaborate, insisting it is a trade secret. A request to visit the office was also turned down.

Sina Weibo users who fall foul of the company's terms of service, such as by posting rumors, risk having their accounts suspended or even deleted in extreme cases.

Tan said that most receive a warning and any offending posts are removed.

However, Qian Jun, a Beijing attorney at Ying Ke Law Firm who specializes in online cases, said rumormongers face fines, detention or even jail time if their behavior has a serious effect on other people or society.

For example, those who spread "terrorist information" online can be sentenced to more than five years in prison, according to Criminal Law.

"Rumors on micro blog are difficult to prevent. Information spreads fast and it's not easy for supervisors to find them all in time," Qian said. "Each netizen should verify the facts before they forward information so they can stop fake news before it leaves his or her hands."