WASHINGTON - Princeton University ordered the evacuation of its New Jersey campus Tuesday after receiving bomb threats to “multiple and unspecified campus buildings.”

Students were alerted to the threat through university’s emergency notification system, and instructed to “evacuate the campus and all University offices immediately” and not to return for any reason.

Similarly, flights at an airport in the US state of Virginia were suspended and the terminal evacuated after a “serious” threat was phoned in, officials said.

On its Twitter feed (@Flack4RIC), Richmond International Airport said it had “received a threat by phone, deemed serious enough to evacuate the terminal as a precautionary measure.”

Sniffer dogs swept the terminal, baggage areas and parking zones, while travelers were advised to check with their airlines for rebooking options, before the all-clear was given.

“Update: #RIC terminal, including airline desks and security screening, re-opened to the public,” tweeted the airport four hours after receiving the undisclosed threat.

More than half a dozen airlines serve the state capital’s airport.

Elsewhere, a “small electrical explosion” prompted a brief evacuation of a concourse at Hatsfield-Jackson Atlanta International Airport in the southern state of Georgia.

“Passengers were evacuated but have returned,” said the airport on its Twitter feed (@Atlanta_Airport). “No injuries reported... Full power has been restored and all operations have resumed.”

Local television station WGCL traced the explosion to a ramp-level maintenance shop.