40-50 people fall ill at Prince George's County courthouse in Upper Marlboro

Emergency crews at the Prince George's County courthouse. (WJLA)

Several dozen people were evacuated from a Prince George's County courthouse Wednesday afternoon after mysteriously falling ill, officials say.

As many as 50 people reported suffering from headaches, nausea and other symptoms inside the courthouse on Main Street in Upper Marlboro.

The people who reported falling ill were located inside the Bourne Wing at the courthouse. Their illness prompted the evacuation of about 500 people from the building.

An initial investigation did not reveal a carbon monoxide leak. Hazardous materials crews are continuing to search for a possible cause.

On Twitter, people who were inside the courthouse said they experienced a "strange odor" before being told to evacuate.

@ABC7News When we told to evacuate, I could smell something really odd. Saw lots of police vehicles around the courthouse

— Dan (@tarvindicated) September 4, 2013

@ABC7News It was just a weird odor - hard to describe, but one you know isn't "normal"

— Dan (@tarvindicated) September 4, 2013

None of the ill people have been taken to the hospital.

ABC7's Greta Kreuz contributed to this report.