BEIJING -- China's food and drug watchdog on Tuesday ordered drug makers to carefully label their bottles with "cautions for athletes" in reference to substances on the doping list.

Yan Jiangying, the State Food and Drug Administration (SFDA) spokeswoman, told a press conference that drug makers would be obligated to withdraw or stop the sale of drugs without distinct labels starting in May.

"For those drugs that have no cautionary labels but are already on sale or left in the factory, pharmacists may add seals or sticky labels of caution to the bottles," she said.

"Drug makers must ensure that customers could see those cautions after purchase."

The doping list referred to the latest version released by the administration in 2007.

China promulgated an anti-doping regulation in 2004, which requires labeling drug bottles with cautionary words for athletes.

Yan said it would provide a safe environment of fair play for the athletes attending the Beijing Olympics and also more easier supervision over the listed substances for the administration.

The SFDA said the move wouldn't be a provisional measure to cope with the upcoming Games, but a start to tighten controls over stimulants and their productions.

She added the SFDA would release a new version of the doping list but didn't give a specific date.

According to the current list, nearly 2,000 drugs sold in China contain stimulants, including many commonly used Chinese patent medicines that professional athletes should use with caution.

The administration launched a nationwide campaign in October to crack down on drug makers who illegally produced and sold stimulants.

The spokeswoman said that so far it had punished 32 businesses in the campaign organized particularly for controlling protein assimilation preparations and peptide hormones. Both are forbidden for athletes competing in the Games.

The SFDA has ordered 18 drug makers to stop illegal production of stimulants and punished 14 drug sellers illegally selling stimulants, revoking licenses of some businesses.

The watchdog and its affiliated departments throughout the country will inspect drug retailers for whether they sell controlled stimulants illegally, according to Yan.

China now has 188 licensed drug makers who may produce protein assimilation preparations and peptide hormones with 355 product permits.