The Associated Press

CLEVELAND - Several computer systems designed to monitor the electric power grid experienced unusual glitches that hindered communication or data in the hours before the nation's biggest blackout Aug. 14, according to a report published Sunday.

The computer woes raise questions about how such misfortune struck separate entities on the same day, the Plain Dealer reported.

The newspaper said its analysis of hundreds of pages of telephone transcripts and interviews revealed that two grid operators and two utilities had malfunctions that could have interfered with ability to detect power surges and failures.

U.S. and Canadian investigators are focusing on failures of a power plant and lines owned by Akron-based FirstEnergy Corp.

The U.S.-Canada task force said Friday that it has yet to determine how the sequence of events before the blackout is related or what role any of the occurrences might have played in causing the blackout to cascade over such a wide area.

FirstEnergy spokesman Ralph DiNicola on Friday said the company's computer system was possibly infected by a virus or worm and said it's working on the issue with the Department of Energy.