Authorities investigate suspicious powder at Kaiser clinic in Antioch

ANTIOCH, Calif. (KGO) -- Authorities in Antioch are investigating after receiving a report of a suspicious white powder found in the mail room of Kaiser's Delta Fair Medical offices.

The incident occurred at 3400 Delta Fair Boulevard in Antioch at around 12:30 p.m.. Contra Costa County Fire Hazardous Materials received a call regarding an unknown powdery substance that came out of an envelope she opened.

The woman who opened the envelope was inside the mail processing room, an isolated area. No patient care happens in that room.

Hazmat crews did several tests to see if the material is hazardous. All preliminary tests have proved negative. Hazmat crews are sending a sample to county health labs.

The mail processing room remains isolated until they receive all clear from county labs. Once they get the all clear, the mail processing room will reopen.