A guerrilla unit blew up heavy equipment Tuesday at Colombia's El Cerrejon mine, which is owned by British, Australian and Swiss interests, marking the fifth attack on the facility this year, but no one was injured, company spokesmen said.

El Cerrejon, located in the northern province of La Guajira and considered the world's largest open-pit coal mine, sustained "substantial damage" in the attack, vice president for sustainability and public affairs Julian Bernardo Gonzalez said.

The attack was staged by the Revolutionary Armed Forces of Colombia, or FARC, which agreed last month to start peace talks with the government to end the Andean nation's 50-year internal conflict, military spokesmen in Riohacha, the capital of La Guajira, said.

Several individuals entered Los Comuneros, an area in the southern part of Cerrejon, around 1:15 a.m. and placed explosives on three large dump trucks, Gonzalez said.

Two of the dump trucks were destroyed, but the charge placed on the third vehicle failed to go off and army explosives specialists are working to deactivate it.

The damage "is still being assessed, but it is extensive," Gonzalez said.

Most of the attacks on the mining complex have targeted the railway that hauls coal to Puerto Bolivar, an export terminal on the Caribbean coast.

Cerrejon is owned in equal parts by Britain's Anglo American, Australia's BHP Billiton and Switzerland's Xstrata Coal.

The mining complex produced 32.3 million tons of coal last year, accounting for 38 percent of Colombia's output of the mineral.

The FARC, Colombia's oldest and largest leftist guerrilla group, was founded in 1964 and operates across a large swath of this Andean nation.

The rebel group is on both the U.S. and EU lists of terrorist groups. Drug trafficking, extortion and kidnapping-for-ransom are the FARC's main means of financing its operations. EFE