KNOXVILLE, Tenn. (AP) -- Congressional investigators say the Tennessee Valley Authority is vulnerable to cyber attacks that could interrupt its vast power production and transmission system.

The Government Accountability Office says the nation's largest public utility must take "sufficient steps" to secure its computer control systems or risk an intended or unintended cyber incident that could affect its operations and nearly 9 million consumers.

The report was prepared for a House subcommittee on emerging threats and cyber security. The panel is worried about the implications for the national power grid. TVA officials testified before the panel in Washington that the agency has heeded the warnings and moved to correct the problems cited by the GAO.

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