Made in China? Police believe some flags may have already been shipped
Police in southern China have discovered a factory manufacturing Free Tibet flags, media reports say.
The factory in Guangdong had been completing overseas orders for the flag of the Tibetan government-in-exile.
Workers said they thought they were just making colourful flags and did not realise their meaning.
But then some of them saw TV images of protesters holding the emblem and they alerted the authorities, according to Hong Kong's Ming Pao newspaper.
The factory owner reportedly told police the emblems had been ordered from outside China, and he did not know that they stood for an independent Tibet.
Workers who had grown suspicious checked the meaning of the flag by going online.
Thousands of flags had already been packed for shipping.
Police believe that some may already have been sent overseas, and could appear in Hong Kong during the Olympic torch relay there this week.
The authorities have now stepped up the inspection of cars heading to the Shenzhen Special Economic Zone and onwards to Hong Kong.
The Olympic torch is due to tour Hong Kong on Friday. It will then travel to a series of cities in mainland China before reaching Beijing for the start of the Olympic Games in August.
Its progress around the world has been marked by pro-Tibet demonstrations in several cities - including Paris, London and San Francisco.
Rallies began in the main Tibetan city of Lhasa on 10 March, led by Buddhist monks.
Over the following week protests spread and became violent - particularly in Lhasa, where ethnic Chinese were targeted and shops were burnt down.
Beijing cracked down on the protesters with force, sending in hundreds of troops to regain control of the restive areas.
But it has since agreed to resume talks with representatives of the Dalai Lama.