Police in Beijing have dismissed rumors of a poisoned gas attack on the subway system, urging commuters to stay calm after false reports circulated on the Internet, Beijing News reported on Thursday.

Reports that men are roaming subway lines 4 and 10 targeting young women with poisonous gas released from cell phones have spread widely on social networking sites sparking panic.

Hai Anjin, an Weibo (twitter-like microblog) user who travels on line 10 wrote online that she ran into the subway at Jinsong station where a "weird" man set beside her, holding up his cell phone, and soon afterwards, she "felt dizzy and numb" after inhaling some "odorless air".

A college girl named Wang Jing (alias) penned a similar story after claiming she encountered the same scenario on May 15, which was posted on Renren.com, China's Facebook, and reposted thousands of times.

Police say the panic is unnecessary. "Being drugged by gas needs a large dose, and the speculation of cell phones sending gas makes no sense," a policeman said adding there're lots of monitors in subway stations and supervision is tight and strict.

Health experts also claim gas poisoning can only happen with a heavy dose and long-time inhalation.

"Even if there were people who inhaled poisonous gas, there's no chance they would be able to walk consciously for one or two minutes afterwards." said Wang Yuan, vice director of anesthesiology department of Chaoyang Hospital in Beijing.