Authorities said the blackout was caused by a failure at an electricity substation. They repaired the grid later that day. Reports of an attack by left-wing rebels who have bombed oil pipelines and power installations were discounted.
Mobile telephones went dead and Colombia's stock market suspended trading for about 90 minutes due to the April 26 blackout.
"It appears to have affected all of the country," President Alvaro Uribe told local radio.
Firefighters said they were rescuing at least 10 people trapped in elevators in the capital Bogota as police poured into the streets to direct traffic at intersections where 10,000 stop lights stood powerless.
Colombia is in a four-decade-old war against insurgents who say they are fighting to narrow the wide gap that separates rich and poor in this Andean country of 42.5 million people.
"The blackout was caused by a failure at an energy substation in northern Bogota. We do not know what type of failure it was," Manuel Maiguashca, vice minister of energy and mines, told reporters.
Hospitals and airports operated normally using their own electricity generators while dairy and meat producers, restaurants and households worried that their refrigerated foods would go bad.
"Disruption of the productive sector is minimal because most industrial plants in Colombia have their own generators," a spokesman for the National Industrial Association said.