According to the local MarinIJ, California Highway Patrol officers said:
"Our officer drove by the first one on Highway 37 and did a double take," Barclay said. "He went back and tried to remove it, but it was put up with tamper-resistant bolts."
Eventually Caltrans had to be called to remove it. By Monday night all the signs were down.
"They were very professionally done, someone knew what they were doing," Barclay said.
The signs were in black and white and even had reflective material. As best as can be determined the signs were put up late Sunday night or early Monday morning.
The CHP is investigating the case and trying to determine where the signs were made in hopes of nabbing the perpetrator.
"The problem is people might slow to look at these things, or to take pictures, and the next thing you know we are responding to an accident," Barclay said.
Barclay noted the signs violate the California Vehicle Code, which prohibit unauthorized signs from being posted on highways.