MILAN, Jan 11 (Reuters) - Energy group Eni said on Tuesday an incident at one of the furnaces at a bio-refinery in southern Italy had triggered columns of smoke but had caused no damage to people or to plant. "At 1330 today inside a furnace of the Ecofining plant at the Gela biorefinery there was a technical error that caused smoke for several minutes but with no consequences for people... or other plants at the refinery," Eni said in a note. The biorefinery at Gela, located in the southern island of Sicily, has a capacity of up to 750,000 tonnes per year of biofuel.