Authorities are warning of possible terrorist threats around the July 4 holiday, several law enforcement officials told CNN on Friday. The Department of Homeland Security, the FBI and the National Counterterrorism Center issued a joint intelligence bulletin to law enforcement across the U.S. The bulletin doesn’t warn of any known active plots. But it serves as a general warning of heightened threats. It says extremists could launch attacks tied to Independence Day or in reaction to perceived defamation of the Prophet Mohammed.