U.S. authorities are tightening up domestic security measures ahead of a possible U.S. military attack on Syria.
The FBI and the Department of Homeland Security are warning of a higher risk of cyber attacks after months of similar disruptions by hackers known as the Syrian Electronic Army.
Warnings from Iranian officials that any U.S. attack on Syria could be met with retaliation has also prompted warnings of possible terror threats in the United States or its interests abroad, U.S. law enforcement officials said.
FBI officials have asked agents around United States to focus on ongoing investigations related to Syria and the surrounding region, checking in with contacts and informants, and "redoubling their efforts," as one official said.
Iran and the Lebanese group Hezbollah have intervened in the 2-year-old Syrian civil war on the side of President Bashar al-Assad's regime. The United States has blamed al-Assad's regime for alleged chemical weapons attacks that have killed scores of civilians.
Hezbollah is known to have extensive fundraising operations inside the United States, and authorities often worry those assets could be used for terrorism.
Unlike previous U.S. military operations against Libya and Iraq, which prompted the FBI to conduct thousands of interviews with exiles living in the United States, FBI officials say the Syrian crisis isn't prompting such a move this time.
Instead, law enforcement officials say they are trying to focus on cases already under way and working to develop any new information that signals possible retaliation against the United States.
The Syrian diaspora in the United States amounts to fewer than 150,000 people with Syrian ancestry, according to 2010 U.S. Census estimates. Syrian immigrant communities in Pennsylvania, Illinois, New Jersey and elsewhere tend to be longstanding.