Gonzalez says the department is on "high alert" because it's not clear whether whoever placed the flyers intended to target law enforcement or whether they were placed at random. It also wasn't clear whether the flyers could have been placed in other locations.
The sheriff's office released a photo of the flyer and urged anyone who sees something similar not to touch it and to call 911.
Gonzalez warned the opioid is deadly and can be easily transferred.
The Harris County Hazmat team is evaluating the scene at the Houston facility.
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