WINDSOR, Colo. (CBS4)– Authorities in Northern Colorado are investigating three more cases of shattered windows, bringing the total number to eight since April 21.

There were three shattered windows reported on Wednesday.

The Larimer County Sheriff’s Office investigated a passenger window that shattered on Interstate 25 near Mile Marker 257 about 11 a.m. The driver was traveling in the northbound right hand lane when it happened. Investigators said if the window was struck with a projectile, it would have come from the east side of the highway. They have not determined what caused the window to shatter.

In another case, a woman was driving along a frontage road along I-25 near Windsor in Weld County when her passenger window shattered.

She told authorities that she had been avoiding I-25 because of the mystery surrounding the shattered windows.

“It’s pretty scary. We live right next to the highway so we have to take the frontage road everyday so there is no other way to go. It’s pretty unnerving to drive everyday and know you might get shot at,” said driver Brady Collins.

RELATED: Woman Shot While Driving On I-25: ‘I Don’t Understand, But I’m Trying’

In another incident, a woman was driving southbound on I-25 south of Wellington when her back window shattered. Deputies are investigating that incident. They said so far, they haven’t determined what caused it to shatter. The woman was not injured.

A driver remains hospitalized after a bullet came through her window last week. There are also cases under investigation in Loveland, Mead and Keenesburg. The struggle now is trying to find a common link in the cases.

State troopers and deputies on Tuesday inspected the pickup truck involved and didn’t find any bullet holes, or bullets lodged. That leaves the shattered glass scare, like most of the others, a mystery.

“Glass just shattered and just went all over,” said Randy Lingbloom from Cheyenne, Wyoming.

He wasn’t hurt. He was in the left lane driving southbound from Cheyenne to Lafayette when his window shattered as he passed the Budweiser plant in Fort Collins.

So far authorities have only been able to explain one of the bizarre incidents. Last Wednesday someone shot out Cori Romero’s car window as she entered the highway near Fort Collins, seriously injuring the 20-year-old.

Romero had called 911 because she thought she had been in a crash near Fort Collins before realizing someone actually shot a bullet through her sedan window, striking her in the neck.

Deputies still have no leads in last week’s shooting, and there’s still a possibility at least some of the broken windows are just a coincidence. But since authorities can’t prove they aren’t shootings, drivers — especially along I-25 — are on alert, and on edge.