Authorities have warned that groups and individuals could be planning the types of violence and destruction seen last week at the U.S. Capitol in Washington D.C.
All members of the Philadelphia Police Department are on notice to work through Thursday. Commissioner Danielle Outlaw said, while there are no specific and credible threats to Philadelphia right now, officers are still prepared.
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The Office of Emergency Management in Philadelphia was also activated on Saturday.
Capitol police in Delaware are working security around the clock in Dover.
And in Trenton, New Jersey, police are working with federal and state agencies, but as of Sunday night, all remained quiet.
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Authorities closed the road leading to the golden-domed building that houses legislative and other New Jersey state offices. The building, which is one of the oldest statehouses in America, dating in part to the 1700s, had already been barricaded because it's under renovation.
"There's more skateboarders than protesters. So that is really good," Trenton Mayor Reed Gusciora on Sunday.
He said local and state authorities were working with the FBI, and that there were no specific threats, echoing what Gov. Phil Murphy had said earlier.
"So it was the unknown," Gusciora said. "You can't take any chances."
There were few signs of uniformed police, too, which Gusciora said was by design.
"We don't want to cause any friction, and if there were protesters, usually they become agitated both ways ... but be advised there's all levels of police."
Murphy on Friday ordered state employees to work remotely on Wednesday when President-elect Joe Biden is inaugurated.
He cited general concerns over what happened at the Capitol, when a mob carrying flags in support of President Donald Trump stormed the building. The violence resulted in five deaths and the impeachment of Trump on a charge that he incited the rioters.
At Pennsylvania's State Capitol in Harrisburg, police have already shut down streets.
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They plan to use resources on land and in the air.
"We have partnered with the FBI. We have partnered with National Guard," Thomas Carter of the Harrisburg Police Department said. "We plan on shutting down streets. I can't disclose those streets, but I want to assure the citizens of Harrisburg that nothing will get into the neighborhoods."
The increased security is in response to an FBI memo that warns of potentially violent disruptions at state capitals in all 50 states.
Authorities said they're focused on identifying, investigating and disrupting any plans for violence.
The Associated Press contributed to this report.