ROCKFORD — A Winnebago County sheriff’s deputy’s squad car was totaled early Wednesday by a semitrailer on U.S. Highway 20.

The deputy had responded to a single-vehicle crash around 4:10 a.m. on U.S. 20, just east of Harrison Avenue, where an eastbound vehicle had left the highway and struck a guardrail.

The motorist was inside the deputy’s marked squad car and the deputy was outside investigating the crash when an eastbound semitrailer struck the squad car.

No one was injured, but the squad car was destroyed. The crash is under investigation by the Illinois State Police.

It is unknown if weather was a factor in the crash, but there were numerous reports of black ice and auto accidents on Rockford-area roads early Wednesday, police said.

The National Weather Service recorded a temperature of 27 degrees at 4 a.m. in Rockford. Wednesday’s projected high of 40 degrees was 21 degrees below normal for this time of year, said weather service meteorologist Jake Peter.

Chris Green:; @chrisfgreen