The Durham County Health Department is investigating Bullock’s Barbecue restaurant after 15 people were sickened there last week, officials said Tuesday.

Seven people were hospitalized for dehydration because of vomiting and diarrhea, said Gayle Harris, Durham County health director.

To pinpoint the source of the foodborne illness, inspectors spent three hours Monday examining food preparation and storage at Bullock’s, Harris said. They also are interviewing people who became ill and others who ate at the restaurant since April 20 and didn’t get sick.

Early laboratory results suggest Salmonella as the cause of the illnesses, officials said, but further confirmation at the North Carolina State Laboratory is necessary. The county was sending food and stool samples to the lab for testing.

Bullock’s is a Durham institution that serves walk-in customers and has a booming catering business. Vice President Joe Biden ate at the restaurant in March during a visit to the Triangle.