* Blackout is latest in recent string of power shortages
* Affected mostly northeastern states
* Brazil investing heavily to increase energy capacity
SAO PAULO, Oct 26 (Reuters) - A blackout affected as many as 12 Brazilian states late Thursday night and early Friday according to local media reports, the latest in a string of power shortages that have raised questions about whether Brazil's infrastructure is keeping pace with economic growth.
The power shortage follows two other blackouts in the past two months that affected millions of customers in the northeast, the capital Brasilia, and parts of five states in the country's south and center-west.
``We are taking all the corrective and preventative measures...to minimize this type of occurrence, which is dramatic for all of us and principally for consumers,'' Hermes Chipp, head of Brazil's National Electric System Operator told the Globo television network on Friday. Chipp added that Thursday's blackouts were the result of an equipment fire.
Brazil went through a so-called ``blackout crisis'' in 2001 and 2002 as a drought limited the output of hydroelectric dams. In response, the government forced electricity cuts in certain regions for hours at a time, severely damaging economic growth.
While Brazil has invested heavily in electricity generation since then, it still has a long way to go, with the country planning to build as many as 48 new hydroelectric plants by 2020 to keep up with the energy demands of rapid economic growth.
Representatives from Brazil's National Electric System Operator did not immediately respond to requests for comment.
(Additional reporting by Pedro Fonseca and Sergio Spagnuolo; Editing by Chizu Nomiyama)