WASHINGTON: The US Department of Homeland Security has warned thousands of US utility plants that they could be the targets of “violent extremists,” according to a report Wednesday from ABC News.

On Tuesday the Department of Homeland Security sent out a terror alert titled “Insider Threat to Utilities” that said “violent extremists have, in fact, obtained insider positions” and might use those positions to wage physical and cyber attacks on behalf of Al Qaeda, according to the news report.

The report warns that an insider at a major utility facility, such as a chemical or oil refinery, could help Al Qaeda wage a major attack near the anniversary date of the September 11 attacks.

Officials found evidence among materials recovered during the May US military operation in Pakistan that killed Osama bin Laden, which led officials to believe that the extremist leader sought to repeat the carnage of the September 11 attacks on or around its ten year anniversary.

“The only way you can actually kill the large scale number of Americans that [bin Laden] literally was calculating was through the use of this critical infrastructure,” former DHS chief of staff Chad Sweet told ABC News.

“Based on the reliable reporting of previous incidents, we have high confidence in our judgment that insiders and their actions pose a significant threat to the infrastructure and information systems of US facilities,” the bulletin said.

Last year US officials arrested an alleged Al Qaeda recruit, and the American man had worked at five US nuclear power plants in the Pennsylvania area after passing federal background checks.

According to ABC News, Homeland Security officials were not aware of a specific threat to any particular utility.