SAN JOSE MINE, Chile – The 33 trapped Chilean miners who have astonished the world with their discipline a half-mile underground will have to aid their own escape – clearing thousands of tons of rock that will fall as the rescue hole is drilled, the engineer in charge of drilling said Sunday.

After drilling three small bore holes in recent weeks to create lines of communication with the miners and deliver basic food and medicine, Chile’s state-owned Codelco mining company will begin boring a rescue hole this afternoon that will be wide enough to pull the men up through 2,300 feet of earth.

The first step will be to drill a “pilot hole” similar in size to the other three. Then much larger machine cutters will slowly grind through that hole, forcing crushed rock to fall down into the mine shaft area near the trapped men.

Failure to keep the bottom clear of debris could quickly plug the hole, delaying a rescue that officials say could take three to four months.

“The miners are going to have to take out all that material as it falls,” Andres Sougarret, Codelco’s head engineer on the operation, told The Associated Press in a phone interview.

In all, the trapped miners will have to clear between 3,000 and 4,000 tons of rock, work that will require crews of about a half-dozen men working in shifts 24 hours a day.

The men have basic clearing equipment, such as wheelbarrows and industrial-sized battery-powered sweepers, Sougarret said. The hole will likely end up several hundred yards from their living area in the mine’s shelter, giving the men room to maneuver and store the rocks, he added.

Sougarret declined to estimate how long the work would take, saying it would depend on how each step went.

On Sunday, Mining Minister Laurence Golborne reiterated that it would take three to four months to rescue the men, rejecting local reports citing engineers who said it could be done much sooner.