The President, Mrs McAleese, was forced to abandon the final part of her address to a business breakfast here yesterday when the lights in the hotel failed.
The blackout, which occurred after several short failures, led to a security alert.
The President and Dr Martin McAleese were escorted from the dark room in the five-star Hyatt Regency Hotel by her Irish personal security officers and brought to a safe area as the lifts were out of bounds, while the incident was investigated by embarrassed staff.
They said afterwards that roadworks outside the hotel had broken a cable and cut off the electricity to 20 blocks in the Santiago suburb.
Strangely, the lights went out fully and the microphone went dead just as the President was speaking of the enlightenment brought about by education.
On her last state visit, the President was at the centre of a similar alert. In China in October, she had to be rushed from a building in Shenyang when part of the ceiling collapsed.
At the breakfast organised by Enterprise Ireland for nearly 300 Irish and Chilean business people, Mrs McAleese said the Irish trade mission was the largest ever to Chile. It aimed to promote Ireland as a world-class supplier of goods and services and to allow Irish and Chilean companies to build relationships.
Chile, she said, was a fast-emerging economy and, like Ireland, had moved from being agriculture and natural resources-dependent into a diversified technology economy.
Today's successful companies thought in terms of global customers and global opportunities.
Later yesterday morning the President was presented with the keys of the city of Santiago by Mayor Joaquin Lavin.
In fluent Spanish, she spoke of the importance of the business delegation that was accompanying her and of the Bernardo O'Higgins monument in Dublin.
She praised the mayor and councillors for the great restoration work they had done on the City Hall since it was practically destroyed in the 1985 earthquake.
Dr McAleese was presented with a gift of silver spurs, although, as the President was overheard to remark, he didn't have a horse. The Irish party - including Minister of State Michael Ahern and Mrs Ahern and the Ambassador to Chile, Ms Paula Slattery - were entertained in the marble hall of the building by a troupe of dancers performing the national dance, the cueca.