Authorities say someone dumped the dirty diapers along MacArthur Boulevard in Newport Beach early Thursday morning.
"That's amazing, that's disgusting, terrible," said Mark Soliman of Irvine.
Police say the illegal dumping of dozens of dirty diapers started last year in Newport Beach and Laguna Beach. The diapers were thrown out mostly along Coast Highway in Newport Beach, and within the traffic lanes between the north city limits of Laguna and the Emerald Bay main entrance.
"It's difficult to determine who's doing this. We have contacted the local assisted living facilities and determined they are not responsible for it," said Newport Beach Police spokesperson Kathy Lowe.
Lowe said those facilities have companies that pick up diapers and dispose of them.
"This definitely appears to be someone that's purposely leaving them in those areas because they do occur in the same area each time," Lowe said.
Residents and cyclists are usually the first to have to avoid the mess.
"I would ride around it. You wouldn't want to hit it," said Amir Bastawrous, a cyclist in the area.
The person or persons responsible face a misdemeanor charge of littering, with fines starting at $100.
Anyone with information is urged to call the Newport Beach Police Department (949) 644-3775.