In a second day of violent protests, more than a thousand demonstrators in the southern border city of Yacuiba swarmed a pipeline control station owned by Transredes, a subsidiary of Royal Dutch Shell PLC (RDSA), breaking windows and setting fire to two company cars.

"This is out of control," Gualberto Duran, president of the Yacuiba Civic Committee, which helped organize the protests, told The Associated Press.

Though Transredes engineers had fled the site, the protesters managed to shut the pipeline valves, cutting off most of the 5 million cubic meters of natural gas Bolivia exports each day to Argentina, said presidential spokesman Alex Contreras.

Contreras said that the shutdown would cost the country some $1.5 million in revenue daily. Two neighboring provinces of Bolivia's gas-rich southern state of Tarija are locked in a dispute over the Margarita field, still in its exploration and development stage but potentially one of the country's largest.

The field straddles the poorly defined boundary between the O'Connor and Gran Chaco provinces, and each is demanding a larger share of the field's eventual royalties.

"I can't understand why two provinces in the same state would be fighting constantly," President Evo Morales said Wednesday in La Paz. "I ask our brothers and sisters in the region to quit fighting over internal problems or money and pacify the area."

On Wednesday a mob of hundreds of protesters also ambushed and disarmed some 50 police sent to Yacuiba to restore order. Yacuiba city employee Jorge Arias Soto said that the weapons were being held at City Hall to keep them out of the protesters' hands.

The government has called for the two provinces to send representatives to the capital, La Paz, for negotiations scheduled for Friday.

More than 2,000 protesters demanding a resolution to the boundary fight on Tuesday attempted to seize pipeline control stations in Yacuiba and the nearby city of Villamontes, both in Gran Chaco province. But the protesters were driven back by soldiers with tear gas and rubber bullets.

At least 20 people were injured in the two protests, and Tarija Gov. Mario Cossio confirmed Wednesday that one Villamontes protester bled to death from an apparent bullet wound in his leg.

Another eight protesters were injured in clashes in Yacuiba on Wednesday. Bolivian government officials have criticized Cossio for failing to resolve the conflict.

The Spanish-Argentine company Repsol YPF (REP) holds a majority stake in the Margarita field, with the U.K. company BG Group (BG.LN) and Argentine company Pan American Energy each owning a minority interest.