By JEFREY PATTIRAJAWANETIMIKA, Indonesia (AP) â¿¿ Rescuers have found four bodies and rescued 10 of the dozens trapped underground after a tunnel caved in at a giant U.S.-owned gold and copper mine in eastern Indonesia, police said Wednesday. The search continued for around 27 other workers a day after the cave-in, Papua police spokesman Lt. Col. Gede Sumerta Jaya said. The collapse occurred Tuesday morning at the Grasberg mine in remote Mimika district in Papua, the easternmost province in the vast archipelago nation. "We don't want to be careless because the terrain surrounding the old tunnel is prone to collapse," he said, adding the cause of the cave-in remains unclear. All of the workers are men, and many of those rescued suffered cuts and broken bones, Sumerta said. The mine is owned by Phoenix, Arizona-based Freeport-McMoRan Copper & Gold Inc. A statement from PT Freeport Indonesia, a subsidiary that runs the mine, said a tunnel in an underground training area located outside the entrance to the mine collapsed. The company believed some 40 employees and contract workers were in a classroom in the tunnel when the accident happened, and three workers managed to escape unhurt on their own. "The rescue process is difficult and will take some time to complete," the statement said. "Our thoughts and prayers are with our fellow employees and their families as we proceed with rescue efforts." More than 20,000 workers are employed at the mine. In 2011, production was crippled when 8,000 unionized employees walked off the job after demanding higher pay. The strike ended after the company agreed to a 37 percent wage hike and improved benefits. The restive province holds some of the world's largest gold and copper reserves.