A wildlife refuge specialist steps out of an air boat onto the Salton Sea shore, which was littered with dead tilapia.

A wildlife refuge specialist steps out of an air boat onto the Salton Sea shore, which was littered with dead tilapia. (Arkasha Stevenson / Los Angeles Times / September 10, 2012)

The mysterious sulfur or rotten-egg smell wafting across Southern California Monday morning is befuddling officials who have been responding to calls from the public.

Lt. Angela Shepherd of the Crescenta Valley Sheriff’s station said that calls had been coming in from La Cañada Flintridge, La Crescenta, Montrose and Glendale.

Shepherd said that the smell was likely caused by sulfur or methane gas , and the L.A. County Fire Department is investigating the odor.

Los Angeles Fire Department spokesman Brian Humphrey said his department has received hundreds of phone calls — including some to 911 — about the odor, which he said has been detected from the Palm Springs area to Simi Valley.

Officials said the department has called the Air Quality Management District.

"They are aware of the odor and are investigating," Humphrey said. "We are not aware of any specific hazard associated" with the odor.

There has been some speculation that the odor is caused by the Salton Sea, where the annual die-off of fish often causes a foul smell. But the Riverside Press-Enterprise reported that officials at the Salton Sea said they don't think the die-off is responsible and that air quality officials are investigating.

The smell was most pronounced in parts of the Inland Empire, which is upwind from the Salton Sea.

-- Andrew Blankstein at the L.A. Times, with Daniel Siegal, Times Community News

Twitter: @ValleySunDan