The leak was in the vicinity of Hillsborough and Pogue streets, and authorities evacuated some buildings in the area.
The incident was reported around 10:30 a.m. outside the Silvia d' Italia Gelato Cafe, which is across the street from North Carolina State University's D.H. Hill Library.
Crews are working to repair the line. Hillsborough Street reopened to traffic just after noon.
No injuries were reported.