Homeland Security Secretary Jeh Johnson says national security officials are “very definitely” concerned about violent demonstrations breaking out at both parties’ national conventions this month.

“I am concerned about the possibility of violence,” Johnson said Thursday at a hearing on Capitol Hill. “I think we have to be concerned about things getting out of hand, very definitely.”

House Homeland Security Chairman Mike McCaul (R-Texas) questioned Johnson and other top national security officials about what they are doing to protect against “fringe groups” that have “directed people to come to Cleveland and bring their weapons.”

Johnson said he will personally inspect security measures in Cleveland on Friday and in Philadelphia on July 22.