By 10:30 p.m., crews had located the leak at 300 West and South Temple and were doing a "small patch on it," said Salt Lake City Fire Capt. Reed Stringam.
The small leak was on a six-inch gas line buried about four feet underground. Crews had to dig through two layers of concrete to get to the pipe before they could begin searching for the leak.
Stringam said traffic in the area was affected all afternoon and would be until early Friday morning.
The cause of the leak is unknown. However, Stringam said crews noted there was a leak near the same area once before.
TRAX authorities said the leak caused service disruptions between the City Center stop and Salt Lake Central. Utah Transit Authority spokesman Gerry Carpenter said a bus bridge going from City Center and Salt Lake Central was put in place for commuters at the time of the leak and continued through the evening.
Tribune reporter Janelle Stecklein contributed to this story.