Chinese hackers have infiltrated a sensitive U.S. Army database that contains information about the vulnerabilities of thousands of dams located throughout the United States. The hacking of the U.S. Army Corps of Engineers’ National Inventory of Dams (NID) has raised concerns that information gathered in the attack could help China carry out a cyberattack on the national electrical power grid.

An unauthorized user traced to China hacked the NID database in January but wasn’t discovered until sometime in April.

Pete Pierce, a spokesperson from the Corps of Engineers, confirmed the attack but did not provide specific details.

“The U.S. Army Corps of Engineers is aware that access to the National Inventory of Dams (NID), to include sensitive fields of information not generally available to the public, was given to an unauthorized individual in January 2013 who was subsequently determined not to have proper level of access for the information,” Pierce said in a statement to the Washington Free Beacon.

Pierce added that the access was immediately blocked once discovered, and that the NID is looking to bolster security to the database.

There are about 8,100 major dams in the U.S., and the NID has information about all of them, including the number of casualties expected if a dam were to fail.

In addition to causing a major disruption to the national power grid, hackers could access the systems that control a dam’s turbine generators. A computer mistakenly started one in a Russian damn in 2009, killing 75 people and destroying eight of the nine other turbines in the dam.

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