(CNN) -- Peru's president arrived Tuesday night at a mine in southern Peru, where he was expected to lead an operation to reach nine trapped miners.
"We have been able to talk with the miners. Their spirits are quite high," President Ollanta Humala told reporters outside the mine.
But more work needs to be done before the rescue begins, Humala said. Engineers were working to make sure the mine was secure "so there are no victims," he said.
"Those same engineers tell us that we have to wait a few hours. They haven't said how many," the president said.
The miners have been stuck since Thursday in the wildcat Cabeza de Negro mine in southern Peru.
Earlier Tuesday, one of the mining engineers in charge of the rescue declined to give a specific time frame for the operation.
"We can't say how long it will take right now to get them out, but I can guarantee that they are alive, that they are in good health, and that ultimately they are going to be freed alive," engineer Carlos Bejarano said.
A cave-in over the weekend complicated efforts.
"It's very complicated work. We're taking into account all the necessary security measures to avoid risks among the rescuers themselves," said Cesar Chonate, a regional head of Peru's civil defense agency, the state-run Andina news agency reported.
Video from state-run TV Peru showed workers, wearing hard hats and headlamps, loading rocks into a pushcart by hand.
It was not clear what caused the initial collapse.
The miners have been getting oxygen, food and water through a tube, which has also allowed them to stay in contact with people above ground, Andina reported.
Peruvian Mining Minister Jorge Merino was also in the area and appealed to mining companies for their expertise, according to a statement from his office.
Mining is big business in Peru, which is a major world producer of copper, silver, gold and other minerals.
"The important thing is that the nine people are alive. We won't abandon them," Merino said.
The ordeal stirred memories of a 2010 Chilean mine collapse in which 33 men were trapped underground for 69 days. All those miners were rescued, pulled one by one from hundreds of meters beneath the Earth's surface with a specially designed capsule.