COTABATO, Philippines (Xinhua) — Two Filipino miners died while two others went missing yesterday after they were trapped and suffocated inside a tunnel in a gold-rich village in South Cotabato province, officials said today.

Local rescuers have retrieved the remains of two victims, Toto and Gary Olin, after the incident was reported to authorities around 5:00 p.m. yesterday in T’boli, South Cotabato, Ramon Ponce de Leon, the province’s environmental management office chief, told reporters.

Ponce de Leon said the victims were suffocated and their siblings working with them went missing underground in a gold mine in Kematu village after a sudden power failure reportedly cut off the tunnel’s oxygen supplies.

“The rotational brownout in Mindanao (made) their machine providing oxygen malfunctioned,” he said, adding that rescuers started a search and rescue operation for Boy and Adel Olin, who were still missing.

Senior Insp. Marvin Dua-Dua, chief of police in T’boli, said they would do everything to locate Boy and Olin.

For her part, Bai Zorahayda Taha, regional director of the Department of Social Welfare and Development, said she had instructed her staff to provide assistance to the victims’ family.

In T’boli, other residents are engaged in sluice mining where they move the soil for easier extraction of gold particles by pouring large volumes of water until the soil washes down to box- type diggings called sluice boxes.

The boxes have screens that are used to separate the fine gold particles from the soil and pebbles.

The miners gather the accumulated gold particles, place them in a container and extract the gold with a pan using mercury.

The area where the incident happened is not far from Tampakan town, also in the province where SMI, a mining company, is exploring gold and copper deposits in the boundaries of South Cotabato, Sultan Kudarat and Davao Del Sur.

The company is partly owned by Australian-listed firm Xstrata Plc., a subsidiary of the Switzerland-based mining group Xstrata. The Tampakan mine, which SMI has been developing, is Xstrata’s largest copper development project in Asia.

It is considered one of Southeast Asia’s largest untapped copper mineral resources with an estimated yield of 11.6 million tons of copper and 14.6 million ounces of gold.