Chemical leaks at a Tennessee cheese factory sent at least 28 people to the hospital on Wednesday after valves at the factory malfunctioned.

The fire department in Greeneville was dispatched to the La Quesera Mexicana, LLC cheese factory in response to a call received at 7:15 a.m., Greeneville city manager Todd Smith said at a press briefing on Wednesday. Greeneville is a town of over 15,000 people around 70 miles from Knoxville.

Six employees were initially sent to the hospital after authorities determined they had been exposed to anhydrous ammonia, a dangerous gas that can irritate and burn the skin, mouth, throat, lungs and eyes, according to the CDC. Authorities determined that the leak came from a broken valve on the outside of the building that was fixed on site, Greeneville fire chief Alan Shipley told USA TODAY.

But nearly three hours after the first call, another 911 call from the factory reported a second, separate leak that sent at least 22 more people to the hospital, Shipley said. An additional 53 employees were also checked for symptoms of exposure.

The fire department announced there was no risk to the public, but asked locals to stay away from the area. By around 1:30 p.m., the site was successfully cleared of the gas, Shipley said.

Shipley said the Fire Department is not certain what caused the two leaks, but the factory owners were investigating.