Three sick, 20 quarantined after envelope with suspicious substance opened in Alameda

ALAMEDA, Calif. (KGO) -- Officials said three people became sick and at least 20 people were quarantined as a precaution after an employee opened an envelope containing a powdery substance at the Customs and Border Protection office in Alameda.

Officials said nothing was found inside the building. However, three employees complained of dizziness and nausea.

Respond teams were at the scene for four hours.

Employees from the U.S. Customs and Border Protection office were all evaluated. At least one woman who was evaluated was taken to the hospital.

Hazmat crews that went inside the building had to be decontaminated just as a precautionary measure. "Initially when the person opened the envelope, they then put the envelope down, they moved to file some things. Things got spread around so there's potential that it spread around in the building, that's why we evacuated everybody from the complex," Alameda Fire Department Chief Rich Bombeck said.

Police said nothing was found and the building is safe.

Officials are investigating what caused three employees to become sick.