Initially the power blackout was explained by the Electricity Generating Authority of Thailand to be caused by the power transmission cables at its Mae Moh power generation plant in Lampang were disconnected from the cabling system.
It was not immediately known what caused the disconnection of its 230 kV power cable but EGAT said the problem has been fixed and the electricity supply was back to the system before noon today.
The electricity blackout affected five upper northern provinces which include Chiang Mai, Chiang Rai, Lampang, Lamphun and Phayao.
All businesses were affected by the blackout since 10.00am.
It was not immediately known how much damages the businesses suffered from the power blackout.