DALLAS (CBSDFW.COM) – Five people were taken to the hospital in April of 2010 after drinking iced tea at a North Texas restaurant that had been laced with sodium azide.

Nothing was said about the incident at a Pottbelly Sandwich Shop location in Richardson at the time. Chief of Medical Toxicology at UT Southwestern Dr. Kurt Kelinschmidt handled the testing of the tea and tells KRLD that there was a decision made to not alert the public. He says they believed the announcement would create unnecessary panic.

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“There was a lot of discussion at the time about whether or not this was an item that we needed to get out to the general public,” says Kleinschmidt. “Very early on, everything pointed to this being an isolated incident and not related to a more general problem with the water supply.”

Kelinschmidt says they narrowed the contaminated tea to one specific urn in the restaurant.

The criminal investigation was handled by the Richardson Police Department. Officer Kevin Perlich says it was clear to investigators that someone had intentionally put the industrial chemical into the tea urn.

“Was it an employee? Was it someone from the outside? Extensive interviews were done,” says Perlich, “but we were never able to determine where the substance came from or who may have tampered with the tea.”

Pelrich says the case has since been closed, and that there have not be any further reports of people being poisoned with Sodium azide.

According to the Centers for Disease Control and Prevention, says this case is “the first detailed report of sodium azide poisonings at a public venue.” It is through the CDC’s recent report  that details about the April 2010 incident is now being made public.

The five victims have since fully recovered.

Chicago-based Potbelly says that they cooperated fully with the investigation and have since installed tamper-proof covers on the tea urns in its restaurants.

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