The Hill reported Napolitano said at a House Homeland Security Committee hearing Wednesday she was not aware of any specific or credible plans by the group to attack U.S. targets.
But she told lawmakers that department officials are in regular in contact with the FBI and had a "very large" conference call this week with Jewish community leaders nationwide and "remain in constant touch" with them.
"We share your concern about Hezbollah," Napolitano told the committee. "We are constantly monitoring their activities around the world. We're working very closely with the FBI and the [intelligence] community in this regard. And in addition we are reaching out to particularly the Jewish community across the country who have been the intended targets in the past."
The Hill noted authorities are investigating bomb attacks in India and Thailand and a failed attempt in the Republic of Georgia. Israel has blamed Hezbollah and Iran, which the United States says provides financial support to Hezbollah.
"Now with the increased tension in the Middle East, I believe that there's a growing threat from Hezbollah," said committee Chairman Rep. Peter King, R-N.Y., who said Jewish constituents in his Long Island district have expressed growing concern. "Certainly I know I have been contacted by local police, also by local houses of worship, especially by synagogues."
The United States considers Hezbollah a terrorist group.