COPIAPO, Chile (AFP) – Engineers began drilling a rescue shaft to 33 trapped Chilean miners, but officials warned it will likely be Christmas before their ordeal is over.

The giant, Australian-made “Strata 950” excavator began work at 10:25 p.m. (10:25 a.m. Tuesday in Manila), according to a government source, who spoke to AFP on condition of anonymity.

The drill will first bore a 33-centimeter (13-inch) wide pilot hole. This must then be doubled using a special drill bit to 66 centimeters – wide enough to lower a rescue capsule down to pull out the miners one by one.

The process will be painstaking and delicate, and operations at the mine, located some 800 kilometers north of Santiago, could take between three to four months, the Chilean government has said.

After 25 days languishing in hot, dank conditions in the San Jose gold and copper mine, some of the miners have developed fungal infections and body sores and others are exhibiting signs of depression.

During the lengthy shaft drilling, the men will have to work in shifts around the clock to clear rocks and debris falling from above, all the time hoping the precarious operation does not cause another collapse.

“They will be helping us. They will be giving us clear information on the state of the mine,” said lead engineer Jorge Sanhueza.

The final rescue will be at night to protect the miners from the sunlight. It will take three to four days as each worker must be painstakingly raised over the course of one or two hours from 702 meters (2,303 feet) below.

The miners’ heroic tale came to light when a note scribbled in bold red letters was found tied to a drill probe on August 22, by which time all hope for their survival was thought to have been extinguished.

A captivated nation heard how the miners managed to make 48 hours-worth of emergency supplies last an astonishing 17 days, digging into the ground to get water to keep themselves alive.

After a request from the Chilean government, the US space agency NASA said Monday it would dispatch a team this week to help efforts to keep the miners fit and healthy.