Division Chief Andrew Kellogg said the fire department received multiple calls of a strong odor of gas wafting from the northwest to the southeast through the city.
Kellogg said the odor was first reported near Barcelona Drive and Schulte Road. He also mentioned reports of the odor at Tracy Boulevard and Windsong Drive, where it forced the evacuation of students at Traina School, 4256 Windsong Drive, for a short time while fire crews checked the school buildings.
Kellogg said the students were allowed to return to their classrooms after the fire crews found no odor inside.
Fire engine crews checking local neighborhoods reported that the odor was dissipating as it traveled southwest.
Kellogg said the odor could have been caused by a large release of natural gas because of excess pressure, called "burping," by a facility that uses the gas.
Representatives of the GWF Tracy Combined Cycle Power Plant off Schulte Road told Kellogg the plant had no such releases.
The division chief said that there was no danger of explosion and that the fire department believed the odor was not caused by any natural gas leaks in the city.
The fire department was attempting to see if any facilities near Tracy had reported a gas release.