The incident prompted an evacuation around 4pm at a Brazoria County Justice of the Peace office in West Columbia, Brazoria County Sheriff Charles Wagner said.
The substance turned out to be acetyl carnitine HC1, a harmless powder used in vitamins and various drugs, such as diet pills.
Wagner said the situation started after a resident who lives in a home between Angleton and West Columbia received an envelope containing the white powdery substance and brought it to the West Columbia Police Department. When a test of the substance came back negative for narcotics, they called the Brazoria County Sheriff's Office since the home was in its jurisdiction.
A Brazoria County deputy who went to pick up the envelope accidentally came into contact with the substance and began feeling nauseous and had some irritation, Wagner said.
"And then it kind of snowballed because he went to the JP's office and we have a bunch of people that were potentially exposed," Wagner said. "Really and truly, very few people were actually exposed to it."
Everyone who may have been exposed, including the resident who received the package and a child inside the home, were then taken to the Angleton Danbury Medical Center, where emergency responders set up a decontamination tent and washed down everyone.
Wagner said everyone is OK, including the deputy.
"He had some nausea and some irritation, but I talked to him when first arrived at the hospital. He said he was fine. He was feeling fine now," Wagner said. "And he was probably the most exposed one and he's fine now."
In fact, Wagner says he's not even sure how the deputy who became exposed to the substance suffered those symptoms.
News that the substance was harmless was a big relief for loved ones waiting for word.
"We just had to keep faith that he'd be OK," said Carol Bloomhuff, aunt of the deputy who was exposed to the substance.
The Brazoria County Sheriff's Office says it has contacted the FBI and the Department of Homeland Security since the envelope was received through the mail. The postal inspector's office also has been contacted.
Meanwhile, Wagner has advice for all residents.
"We would hope that anybody who receives a package like that would not open and contact authorities first and say, 'I've got a package that I don't have any idea where it's from, who it's from and what I received it,'" Wagner said. "Had that been done, we wouldn't have had anybody exposed to it 'cause it would have been brought back to our lab and our lab personnel would have opened it up under controlled conditions to take care of it."