Police in the Olympic host city Beijing have seized 221 illegal ticket brokers and 569 tickets for the ongoing Olympic Games, after a crackdown on the illegal business.

Among them 71 people have been detained by the police. Others were released after being given warnings, the Beijing police said on Sunday.

A total of 31 foreigners got involved in the illegal business, among whom three were detained, and 14 people's visa duration in China were shortened.

All confiscated tickets would be hold as the evidence of the cases, the police said.

Beijing police launched crackdowns on ticket scalping near various Olympic venues and subway stations on Friday and Saturday, amid the boom of the illegal business as the tickets have been frantically pursued since the Games opened on Aug. 8.

A Chinese woman was caught on Friday when she tried to sell tickets for gymnastic competitions at prices which were even 10 times of the official ones. She was detained by the police.

A foreign man, whose nationality and name was not disclosed, was detained after he was found selling two tickets at a price of 1,000 yuan (145 U.S. dollars) each, while the price was just 300 yuan.

The police said the man bought more than 130 tickets in Italy and had sold over 60 tickets at different prices after he arrived in Beijing.

The Games' organizing committee has repeatedly warned that "resale of Olympic tickets for profit is illegal" and vowed to "support the authorities to crack down on suspected illegal transactions."

The police also warned that they would step up crackdowns on ticket scalping.