Copiapo, Chile (CNN) -- A "Plan C" oil drill to reach 33 miners trapped in Chile is scheduled to start in earnest early Wednesday amid hopes it will provide a faster solution than the other two methods used.
But officials do not know how long it will take the drill, normally used in to drill for oil, to reach the men trapped 700 meters (2,300 feet) underground.
By Wednesday afternoon, the Plan C drill reached 40 meters, officials said.
The plan is for the new drill to descend vertically for at least 40 meters before turning at an angle to reach the underground ramp that leads to the miners, said Andre Sougarret, manager of the state copper mining company.
Sougarret said that attaching directional motors to the drill would slow it to a speed of 1 meter per hour, adding that 20 to 30 meters per day "would be a good average."
Under optimal conditions, it is capable of drilling 1,000 meters in 24 hours, said Juan Carlos Marin, a site representative for Schlumberger oil services company.
Meanwhile, the Plan A drill was 366 meters in, and the Plan B drill, which was widening a hole it made, was at 85 meters, Sougarret said.
The Plan B drill was temporarily halted Wednesday after the drill bit came loose and fell down the mine, he said.
"We felt a loss of pressure, and the miners called us to say the bit had fallen into the mine," Sougarret said.
Officials believe that the malfunction occurred after the drill moved from hard rock to softer material. The bit that fell will remain in the mine, and a spare drill bit will be used, officials said.
Government engineers are finalizing designs for three rescue capsules, which will be sent down the completed rescue shaft to extract the miners one by one, according to Sougarret.
The capsules will take 10 to 12 days to build.
Sougarret said the largest of the miners measures 48 inches around the shoulders.
The "design of the capsule is being completed with this in mind," Sougarret said.
Despite the fact that Plan C is capable of significantly higher speeds than drills A and B, Sougarret would not move up the expected date of the miners' rescue.
"My sources are the technical indicators, and we are still working toward the beginning of November," Sougarret said.
Engineers are dealing with hard rock and a much smaller area than they normally encounter, Marin said.
"When we drill for oil, we have a much bigger target area of perhaps 50 or 60 meters. Here we have a margin of error of just 4 meters," he said.
The need for precision in this drilling operation means the drill will move much more slowly, he said, but he gave no precise predictions.
"If we did not have such a specific objective at 700 meters, then we could do this in two days," he said. "But what changes all this is that we have to reach an objective with precision, and so we do not know how long that could take."
For now, the company has told Chilean officials that it could take 40 days to complete the work, he said. He did not say whether time it took to assemble the rig and drill the pilot hole was included in that time frame.
Two other drills are also trying to reach the miners, who have been trapped since the August 5 cave-in. The drills, dubbed Plan A and Plan B, each require two holes to be drilled and have been moving at a rate of 30 or 40 meters a day.
Officials are planning how they will bring the miners to the surface once a bore hole is wide enough for the task. The daunting rescue may require an oxygen-fed cage that will haul them up one at a time.
Previously, officials have said that the workers could be rescued, if all goes well, in late October or early November.
"When I look at their faces on their video they have sent to the surface, I would love to have them out by tomorrow," Marin said.
CNN's Esprit Smith and Patrick Oppmann contributed to this report.