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Caption:WASHINGTON, DC - JULY 02: Security barriers block vehicle access in front of the US Capitol building July 2, 2015 in Washington, DC. Security has been ramped up around the Capitol for the upcoming 4th of July festivities. (Photo by Mark Wilson/Getty Images)
Caption:WASHINGTON, DC - JULY 02: Security barriers block vehicle access in front of the US Capitol building July 2, 2015 in Washington, DC. Security has been ramped up around the Capitol for the upcoming 4th of July festivities. (Photo by Mark Wilson/Getty Images)

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    Officials heighten security, cite terror concerns

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Officials heighten security, cite terror concerns

Officials are increasingly concerned about possible terror attacks over the holiday weekend. CNN's Sunlen Serfaty reports.

Officials heighten security, cite terror concerns

Officials are increasingly concerned about possible terror attacks over the holiday weekend. CNN's Sunlen Serfaty reports.