The FBI and U.S. Department of Homeland Security (DHS) warned law enforcement agencies across the country of possible copycat attacks following the ISIS-inspired attack on New Year’s Day in New Orleans that killed 14 people and injured dozens more.

The two federal agencies issued a public service announcement highlighting the potential public safety threat from violent extremists, to about 18,000 law enforcement agencies across the U.S.

The agencies included local police and sheriff’s departments and warned those who wear the uniform to be hyper vigilant of copycat attacks after the New Orleans attack.

“The FBI and DHS are concerned about possible copycat or retaliatory attacks due to the persistent appeal of vehicle ramming as a tactic for aspiring violent extremist attackers,” the PSA read. “Previous attackers inspired by foreign terrorist organizations (FTOs) who have conducted vehicle attacks in the United States and abroad have used rented, stolen, and personally owned vehicles, which are easy to acquire.”

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The PSA also noted that some of the attackers have used additional weapons such as firearms and knives, to attack individuals once the vehicle stops.

Others have attempted to conceal and pre-position improvised explosive devices (IEDs) to supplement a vehicle attack, the PSA added.

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Not only have attacks been on pedestrians, but they have also targeted law enforcement, military members and crowded public venues like festivals and commercial centers, accessible by roadways.

“We ask that the public remain vigilant regarding possible copycat or retaliatory attacks and report any suspicious activity to law enforcement,” the federal agencies said.

The warning does not provide specific intelligence warning of a specific copycat attack. Instead, it is a general warning to keep people aware.