Barberton - The drilling of the second shaft at Mpumalanga's Lily Mine has been suspended, days after it started.On Monday, Vantage Goldfields spokesperson Coetzee Zietsman said drilling had stopped due to technical challenges."There seems to be a mechanical problem with the drill, because of rust. The mining engineers are on it, and drilling will commence soonest," said Zietsman.The sinking of another shaft is necessary before the search can continue for three mineworkers still believed to be trapped in a container buried under 80m of rock that fell into a sinkhole during a cave-in on February 5.The drilling initially started shortly after midday on Saturday. The mining drill arrived at Lily Mine near Barberton last Thursday on five heavy-duty trucks.It is now 17 days since the fateful Friday when 78 workers were trapped after a central, or crown pillar, collapsed. Seventy-five managed to escape unharmed. Yvonne Mnisi, Solomon Nyarenda, and Pretty Mazibuko are still unaccounted for.Estimates are that it could take at least three weeks before search and rescue operations resume.