About 1,000 gallons of sewage reportedly leaked into the harbor from the utility district's San Antonio Creek Wet Weather Treatment Facility at 321 Embarcadero while an operation test was being conducted at the facility around 11:15 a.m.
Samples were then taken to determine whether the water was safe, utility district spokesman Jeff Becerra said.
Signs were temporarily posted in the immediate area around the spill to inform the public of the "No Water Contact" advisory.
"The main issue with an incident like this is bodily contact," Becerra said. "You just want to make sure that people are not in the water."
Results that came back around 6 p.m. Thursday showed the contamination no longer impacted the water and around 7 p.m. utility district employees began taking the signs down, according to Becerra.