In its weekly bulletin, the OCHA said it had "received reports of looting of houses of displaced people, markets and businesses" in the camp and Kutum town.

CNN: STORY HIGHLIGHTS

The official said the warning was sent in a weekly bulletin to 18, 000 state and local agencies, a lightly classified alert that outlines possible tactics terrorists could use.

CNN: FBI warns of possible deadly floating material

In the FBI's weekly intelligence bulletin, dated Wednesday and sent out to state and local law enforcement offices, the agency said the U.S. government has no "credible threats about specific attacks, " according to a senior administration official who has a copy of it.

CNN: White House urges 'joyous' but vigilant Fourth