Thirty-one people were exposed to a hazardous material Sunday morning at a McDonald's restaurant in Knightdale. Six of those people were taken to local hospitals, according to Jeffrey Hammerstein, District Chief of Wake County Emergency Medical Services. Most had minor symptoms such as burning eyes, nose, and mouth.

It happened around 10:15 a.m. inside the restaurant located at 7141 Knightdale Blvd.

Authorities closed the restaurant until about 1:30 p.m. trying to determine the cause of the symptoms. They have not reached a conclusion.

"Whatever was there is gone," Hammerstein said.

The restaurant's Owner, Gary Thill, released this statement Sunday afternoon:

"Our main concern is always the safety of the our customers and crewmembers and we worked most of the afternoon with the fire department, the haz mat team and the health department to determine what may have caused the situation. I am happy to say that, after a thorough check of every part of the restaurant, authorities were unable to find anything wrong in the ventilation or air quality system in the restaurant."

The investigation continues, Hammerstein said.