MEXICO CITY, Sept. 2 (Xinhuanet) -- A power outage left at least 3 million Mexicans in the southern Yucatan peninsular without electricity on Tuesday, the authorities said.

　　The blackout occurred before dawn in Mexico's southern states of Yucatan, Campeche, Quintana Roo and parts of Tabasco and Chiapas.

　　By afternoon, power had been returned to about 80 percent of the affected area, civil protection officials said.

　　"The preliminary diagnosis is a flaw in a transformer in the Ticul substation (in Yucatan), which kicked into operation the peninsula's automatic protection systems," the Federal Electricity Commission said in a news release.

　　The fault, which automatically shut down power lines, could have been caused by lightning or a mudslide, said the Federal Electricity Commission.

　　The popular coastal resort of Cancun in Quintana Roo state was hardest-hit by the power loss. Many tourist centers used their own generators to keep facilities running. Cancun is to host a major World Trade Organization conference next week. Enditem