Government officials say al Qaeda may be trying to infiltrate critical facilities in the United States, including nuclear power plants, for future attacks.
The Department of Homeland Security issued a report this week warning that sabotage by an insider could give terrorists access to major utility facilities.
"Violent extremists have, in fact, obtained insider positions' at chemical and oil refineries and have 'attempted to solicit utility-sector employees," officials said in the report.
The department said it had no "specific, credible intelligence" of an imminent attack, but that there were a wide range of potential threats and areas subject to sabotage.
"There are a lot of very sensitive facilities where someone can get a job on the inside, can get access to a control room, flip a switch, which (can cause) an electric power grid to short circuit, causes a pipeline to explode," said ABC News consultant and former national security official Richard Clarke.
"If someone were determined and had the right access, the amount of damage that they could inflict could affect thousands of lives," added former Homeland Security official Chad Sweet.
The report was released in response to documents found in Osama bin Laden's compound that revealed the al Qaeda leader was plotting another major attack in the U.S. -- possibly on this year's 10th anniversary of 9/11.
Several facility leaders who received the report say they will put employees on alert for suspicious behavior.