Fitri Pikong & Antara, Mataram – A district office in Bima, West Nusa Tenggara, was burned to the ground along with several motorcycles and cars by a mob of thousands of residents demanding that officials revoke a decree granting exploration rights to mining companies.

The angry crowd also went to a nearby detention house and forced authorities there to release 35 people arrested during a mining protest at Sape port on Dec. 24, 2010.

The mob, drawn from across the province and angry at finding the district office empty, set it and the smaller Elections Commission building ablaze at around 2 p.m.

According to Antara, the demonstration was initially meant to be a peaceful show of anger at District Head Ferry Zulkarnain refusal to revoke a 2010 decree that led to the granting of exploration rights to miner Sumber Mineral Nusantara.

Earlier this week, residents had banded together to demand that officials revoke the decree within five days, but it was unclear exactly when that demand was issued.

Last month, a protest against mining operations in the area turned deadly when police officers fired on demonstrators at Sape port in Bima. Three protesters were killed in that incident and dozens were arrested.

Demonstrators on Thursday, angry at finding Satpol PP and other security forces guarding the empty district office, swarmed into the building, throwing furniture and other items out of the windows before leaving and setting the structure ablaze, police said.

Members of the mob also put the neighboring Election Commission office to the torch.

"From the information that we received, they burned down the Bima district office and the Bima Election Commission office, which is also in that area, along with the goods inside the buildings," said West Nusa Tenggara Police spokesman Adj. Sr. Comr. Sukarman Husein.

Besides the two buildings, police said motorcycles and other vehicles in the area were also set ablaze. "Recent news reports says the smoke is still swirling around the scene. It is not yet known if there's any victims or not," Sukarman said.

After setting the government buildings on fire, the mob marched to the Rutan Raba Bima detention house, and forced guards there to release 35 people arrested during the Sape port protest.

Bima District Head Ferry was reportedly far from the office at the time of the riot, and was in a safe place, according to authorities.