Baltimore police believe three notoriously violent gangs are now working together to "take out'' law enforcement officers.
In a statement Monday, the department called it a "credible threat'' and said members of the Black Guerilla Family, the Bloods and the Crips have formed a partnership against the police.
The department warned other law enforcement agencies to "take appropriate precautions.''
The police statement came as mourners gathered for the funeral of Freddie Gray, who died of a mysterious spinal injury while in police custody.
Police spokesman Capt. Eric Kowalczyk would not say whether the threat is related to the death of Gray. Kowalczyk said the threat announcement has been circulated to law enforcement agencies nationwide.
Earlier this year, Baltimore police said the Black Guerilla Family sent a man into the Northeastern District station house with marijuana, cocaine and a loaded gun to test the station's security.