BHP declares force majeure due to blockades at Cerro Matoso

LONDON, April 30 (Reuters) - BHP Billiton (NYSE: BBL - news) , the world's largest mining company, said on Thursday that union blockades at its Cerro Matoso nickel operation in Colombia had forced it to declare force majeure with some customers.

Unionized workers, who on Thursday said they plan to continue striking, have blocked access to the Cerro Matoso ferronickel mine and processing plant since April 14 to protest a change to 12-hour shifts from eight hours.

Since last week, BHP has been flying some workers into the ferronickel plant with a hired helicopter in order to resume production, at least partially, despite the blockades that the company says are illegal.

"As a result of an illegal union work stoppage and blockade of its plant facilities at the Cerro Matoso operation, it is operating at less than full capacity," a company spokeswoman said in an emailed statement.

"As a result, and, as is normal practice, we have taken the prudent step of issuing force majeure notices to customers and the Colombian State Mining and Environmental Authorities."

Force majeure is an exemption clause commodities suppliers use when they are unable to meet a contractual supply obligation due to factors beyond their control.

"The company will continue to pursue a resolution of this matter, which relates to a change in work rosters within some business units, directly with the union and through legal avenues," she said.

Cerro Matoso's Luis Marulanda, vice president of external affairs, told Reuters a judge had this week given the workers 48 hours to end the blockade, now in its 17th day, but it had still not been lifted by mid-afternoon on Thursday.

Union leader Domingo Hernandez said he had received no such notification and said workers planned to stay on strike for the maximum legally permitted 60 days after which the dispute would be automatically sent to a labor tribunal.

Cerro Matoso is one of the assets that form BHP's proposed spin-off company South32.

South32 is due to list on May 18, pending approval from BHP shareholders on May 6.

BHP said that it does not expect the current union blockade to have a material financial impact on BHP Billiton or South32. (Reporting by Silvia Antonioli and Eric Onstad, additional reporting by Peter Murphy in Cartagena, Colombia; editing by Jane Merriman and Ted Botha)