Even accounting for holiday and weekend travelers, highway construction and the occasional fender-bender, traffic through Marin County into Sonoma County was worse than usual Saturday, the CHP said.

While Saturday marked the first day of weekend visitors to the new Graton Resort & Casino in Rohnert Park, CHP officials in Marin County would not say hopeful gamblers were to blame for bumper-to-bumper traffic through the Novato Narrows just south of Petaluma.

"We don't know where all these people are going that were just passing through our area," said a CHP spokesman Officer Andew Barclay. "It's bigger than usual backup, bigger than a normal weekend."

Traffic flowed freely on Highway 101 through Petaluma and Rohnert Park throughout most of the morning. But real-time traffic maps showed significant delays through the Novato Narrows and Petaluma throughout the afternoon.

"I don't know if that's casino-related, it is a big beautiful day. I wouldn't jump to any conclusions just yet," Officer Nanad Gorenec.

Gorenec said extra CHP officers will be working casino-related details all weekend from 2 p.m. to 2 a.m.

"They're only assigned to traffic control for the casino this weekend."