Rescue workers in Mexico are having more trouble locating 65 coal miners who have been trapped underground since last weekend.

Government officials say rescue teams reached the spot where two miners were believed to be trapped, but found no sign of the men.

Officials say the rescue teams are encountering higher toxic levels of methane gas as they advance into the mine.

Rescue workers prepare to enter a Mexican coal mine after a blast on Feb. 19, 2006. (AP Photo/Juan Montano)
Rescue workers prepare to enter a Mexican coal mine after a blast on Feb. 19, 2006. (AP Photo/Juan Montano)

Weary rescue workers say they will continue digging through hundreds of tons of rubble in hopes of finding the miners.

On Sunday morning, eight other workers were injured when gases ignited at the mine in a remote area of northern Coahuila state near the border with Texas. The 65 trapped miners were in several areas about 300 metres below ground.