Hazardous materials teams have not been able to determine what substance caused breathing difficulties for eight people at the Mary Grizzle State Office Building Tuesday afternoon.
Three of the eight were sent to the hospital, and the rest were treated by paramedics in the parking lot and sent on their way.
Investigators said a man with a partially opened backpack walked into the building shortly before 4 p.m. When he left, several people started complaining about respiratory issues.
Witnesses gave police a very vague description of the man.
"A shorter white male, wearing a white shirt with a baseball hat, and a slightly opened backpack," said Lt. Paul Amoedo with the Largo Police, Department.
Largo Fire Rescue got the call around 4 p.m. Dozens of firefighters suited up and went in to evacuate 200 to 300 people.
"After our HAZMAT teams made entry they did take several samples," Assistant Fire Chief Doug Swartz said. "They found nothing remarkable initially. There are things that need further testing."
Firefighters shut off the buildings air conditioning and contained the substance to one office on the first floor.
Investigators said there doesn't appear to be any surveillance cameras that could have captured a picture of the man with the backpack.
But detectives are checking log books to see who was in and out of the building all day, and they're interviewing several employees.
Investigators said state authorities and the FBI are assisting in the investigation.
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