Story highlights Officials say the investigation originated from intercepted chatter

Possible threat focused on parts of California, one says

(CNN) The FBI is investigating a possible ISIS-inspired terrorist threat in the United States, law enforcement officials said Saturday.

The investigation originated from intercepted chatter and other intelligence information that led officials to believe a possible plot could be in the works, the officials said.

No arrests have been made. It's not clear whether the threat is real or aspirational.

The exact nature of the threat couldn't be learned. One official said it focused on parts of California where officials stepped up security, a U.S. official said.

The Transportation Security Administration alerted local law enforcement agencies that are responsible for external security around airports, but officials said the possible threat is not necessarily aviation-related.

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