Lifeguards in Encinitas were first to report the strong, pungent odor at about 5 p.m.
The odor was described as a gas-like smell rolling in off the ocean.

Soon after, 10News was flooded with calls. Residents from the coast all the way to Rancho Bernardo and 4S Ranch reported experiencing the smell.
Some complained of headaches and outdoor activities were canceled.

One Del Mar resident who did not want to be identified was inside the library in Cardiff at about 5 p.m. when the gas-like odor filled the entire building with the doors closed.

"There was none when I walked in that door and within 10 minutes, the entire library was filled," she said.

Eventually, she got in her car and drove to try and get away from the smell.

At about 5:30 p.m., the woman parked at San Dieguito County Park and took a photo of what she believes is some kind of aerosol compound she says fell from the sky and coated her car windows.

"I tried to wipe it and it was black and sticky and tried to put my window down and it smeared," she said.

She is convinced it was gas that was dispersing something with an oil component.

Late Tuesday night, 10News received a statement from the City of Solana Beach that read, "Please do not be alarmed. The apparent smell of gas reported from Oceanside to La Jolla is not a leak of gas. The smell is caused by natural occurring condition from the ocean."

Red Tide
No deaths of humans have been attributed to Florida red tide, but people may experience respiratory irritation (coughing, sneezing, and tearing) when the red tide organism (Karenia brevis) is present along a coast and winds blow its toxic aerosol onshore. Swimming is usually safe, but skin irritation and burning is possible in areas of high concentration of red tide.

Originally posted by kaleshchand
How often does it happen? When was the last time it happened?

"It smelled like it was a gas leak," added Maryanne Bache, who lives next door. "And if it wasn't a gas leak, it smelled like propane."
While the source of the smell is still under investigation, San Diego lifeguards said the odor was emanating from the ocean floor off Encinitas and was being carried by the wind.

Tuesday evening, air quality experts from the county theorized the stench might have been caused by rotting kelp.

The Air Pollution Control District says it will begin conducting tests Wednesday. It has special stations set up throughout the county which constantly gather air samples.

A similar "mystery odor" was reported throughout San Diego County last August. While experts conducted air quality tests in the days following, the source of that smell was never definitively determined.