At least two federal buildings in Portland have been closed after a car bomb threat was made.

The officials said on Friday that the FBI was investigating the threat, which was received Thursday. It had warned of the intention to use a car bomb to target federal property in Portland.

Investigators are trying to determine whether the threat is credible, the FBI said in a statement.

The Portland office of the US Bankruptcy Court was closed because of a threat of violence in the area, according to the court’s website.

Demonstrators have taken to the streets of Oregon’s largest city — almost daily — since the May police killing of George Floyd and clashed repeatedly with federal agents dispatched to protect the courthouse.

Protesters this week attacked the US Immigration and Customs Enforcement building in Portland.

People in a group of about 100 late Thursday and before dawn Friday sprayed the building with graffiti, hurled rocks and bottles at agents and shined laser lights at them, Portland police said in a statement.

Three people were arrested, police said in their statement.