A mail carrier in San Bernardino said it smelled like rotten eggs. A woman in Rancho Cucamonga blamed it on dairy cows in Chino. A man in Rialto said he couldn't smell it at all. And about 60 miles west in Los Angeles, curious callers in the north end of the San Fernando Valley were calling the Fire Department seeking answers.

They were among thousands across the Southland on Monday to catch a whiff of what officials said was the result of biological decay, possibly from the Salton Sea, and an unusual wind that pushed it west.

Fontana resident Walter Martinez, 33, may have best described the foul odor wafting through the Inland area.

"It's kind of funky," he said. "If I go outside and take a breath, I cough. I feel an air irritation."

Air quality officials from around the region fielded phone calls throughout the day from residents concerned about the smell.

Field inspectors with the South Coast Air Quality Management District in Diamond Bar spent the day investigating the possible causes of what they described as "widespread sulfur odors."

"Fish kills, algae blooms and other biologic conditions in lakes can cause strong odors," said spokesman Sam Atwood, in a news release. "Industrial facilities such as wastewater plants also can cause sulfur odors. At this time AQMD hasn't confirmed any source as the cause of the widespread odor."

Those who smelled it had their own theories.

"It's awful," said Roberta Marroquin, a 52-year-old Rancho Cucamonga resident. "You know what, I think it's the cows from Chino."

Some experts said the Salton Sea - about 100 miles southeast of San Bernardino - may be to blame.

"It's an unusual wind pattern that sent the Salton Sea smell pattern north," said Jack Crayon, an environmental scientist with the California Department of Fish and Game in Bermuda Dunes. Read more at The Sun