BEIJING (AP) — At least four Tibetans were fatally shot and 30 others wounded when Chinese police opened fire on demonstrators protesting the expansion of a gold mine they blamed for causing environmental damage, a media report said Saturday.

The shooting took place Aug. 17 in southwestern China's Sichuan province not far from the border with Tibet, according to the report from U.S.-funded Radio Free Asia.

The report said the shooting happened when a group of Tibetans was protesting outside the Baiyu county offices in Ganzi prefecture.

Radio Free Asia said its information came from Tibetans living outside China who follow events inside the country.

It quoted them as saying the protesters were upset because heavy equipment brought in for the increased mining operations had damaged farmland.

A policeman at the Ganzi Public Security Bureau said he had not heard of the shooting. He would not give his name and hung up the phone. Calls to the police and government offices in Baiyu rang unanswered Saturday.

A pro-Tibetan independence website, Phayul.com, said three Tibetans had been killed and 30 others wounded when they were fired upon. No reason was given for the different death toll.

It said 100 Tibetans had been protesting outside the government offices.

Ganzi, a deeply Buddhist region filled with monasteries and nunneries, is known for its strong Tibetan identity and has been at the center of dissent for years. It saw some of the most violent protests in the spring of 2008 after anti-government riots in Tibet.

Radio Free Asia said the confrontation came to a head when country officials detained several of the demonstrators who had been protesting for three days. It said two policemen were injured.

Some of the 30 wounded were in critical condition and had been taken to hospitals in the provincial capital of Chengdu, Radio Free Asia said.