Contra Costa County hazardous materials officials said that a leak of "sour water" at a ConocoPhillips refinery in Rodeo was contained Sunday morning.

The leak in the 1.5-million gallon tank was first reported Friday morning. An unknown amount of hydrogen sulfide leaked from the tank, spreading a noxious smell but staying far below established hazardous levels for public exposure, according to county officials.

At least 10 people reported nausea, throat irritation and respiratory symptoms due to the gas leak.

The leak was sealed off early Sunday morning, said Steve Morioka, assistant director of the county's hazardous materials program. A health advisory that was issued Friday was lowered at about 8:30 a.m. Sunday.

The incident remains under investigation, and crews are continuing to monitor air quality in the area.