KNIGHTDALE, N.C. — A McDonald's restaurant in Knightdale has reopened after a haz-mat incident sent six people to the hospital Sunday morning.

Investigators haven't determined the nature or cause of the haz-mat situation, which was reported at 7141 Knightdale Blvd. around 10:15 a.m. Wake EMS crews and Knightdale firefighters and police responded.

Three people were transported to WakeMed, two to Rex Hospital and one to Duke Health Raleigh, said Jeffrey Hammerstein, district chief with Wake County Emergency Medical Services. WakeMed and Rex had treated and released its patients by Sunday evening.

"They had mild upper respiratory complaints, burning eyes (and) mouth," Hammerstein said of the symptoms.

Others who were exposed were checked out by EMS workers in the parking lot, Hammerstein said. All were expected to be OK.

A firefighter was also treated for exposure and released from Rex Hospital, according to Knightdale Fire Chief Tim Guffey.

Phillip Currence, of Charlotte, said he, his sister and a friend were getting coffee when they suddenly noticed customers coughing. Their throats then got itchy, he said, so the three went outside. There, they found more people coughing.

"My throat started scratching, started itching, like not really choking but itching," Currence described. "Everybody went outside, and then I started feeling it."

His sister, Linda Kay Norris, called 911. Currence said he and Norris both started coughing and were taken to WakeMed. They were in stable condition Sunday.

An employee said she also started coughing in the restaurant but was now fine.

Nearby buildings did not have to be evacuated, and employees were instructed to wait outside in the parking lot.

Guffey said the restaurant reopened Sunday evening after a health inspector checked out the facility. The cause of the haz-mat situation remained unknown, Guffey said.

Currence said experiencing a haz-mat situation made for an interesting visit to Raleigh, but he wouldn't hesitate to go the McDonald's again.

"I think it was an isolated incident. Things happen," he said. "If I get a chance to go back to McDonald's, I'll go back tomorrow."