GLENDORA (CBSLA.com) —  San Gabriel Valley residents have been noticing a mysterious black dust blanketing their neighborhoods for the past two days.

Alfred Micallef, who lives in Glendora, said he spent much of Thursday cleaning his patio of a layer of black soot.

“I noticed that the pool had a layer, (too). Like, a blanket of black stuff on it,” he said.

Micallef’s neighbor, Kevin Connard, woke up to the same substance, but on his car.

“You could even see dust being kicked up in the street as the cars went by. It was really bizarre,” Connard said.

The South Coast Air Quality Management District said they received calls about the questionable residue from people living in Azusa, Covina, West Covina, and Glendora.

The AQMD took samples and said the soot is likely soil churned up from the wind during the last couple of nights.

“It just funneled a large amount of wind through these canyons and then when it got into the valley areas it really wasn’t windy, so anything that had been picked up was just deposited,” said Jill Whynot of the AQMD.

The agency said the soil may also be mixed with ash from recent brush fires.

Micallef said he remembers seeing several inches of similar dust after the 2009 Station Fire in the Angeles National Forest.