Updated at 12:35 p.m.

About three dozen workers at the Coffee Creek Correctional Facility were evacuated from the prison’s administration building Wednesday after an employee in the mailroom discovered an envelope containing a powdery substance.

No inmates were taken out of the Wilsonville-based women’s prison, and the facility was placed on lockdown after the discovery, said Stefan Myers, a Tualatin Valley Fire & Rescue spokesman. Four employees in the mailroom were exposed to the substance and were decontaminated, he said.

Jennifer Black, a state department of corrections spokeswoman, said the four employees were taken to a hospital as a precaution. Another 30 workers were evacuated from the administrative building, where the mailroom is.

She said an investigation is ongoing to determine what the substance is. The prison’s heating, ventilation, and air conditioning system was shut down to prevent the spread of possible contamination.

The prison remains on lockdown as of 12:30 p.m. Visitation to the medium-security facility has been cancelled for Wednesday.

Two mailroom workers reported shortness of breath, but the four employees otherwise exhibited no apparent life-threatening symptoms while being evaluated. Someone called 911 about the suspicious package a little before 8:30 a.m.

-- Everton Bailey Jr.

ebailey@oregonian.com | 503-221-8343 |@EvertonBailey

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