FORT COLLINS, Colo. -- A string of unsolved sexual assaults in Fort Collins has officials at Colorado State University looking for ways to keep students safe -- especially since classes are set to begin later this month.

Most of the residence halls at CSU have no air conditioning, 7NEWS reported. So when students start moving in next week, they'll most likely be leaving their windows open to stay cool.

To keep them safe, the university will be installing special locks that will allow the windows to open only part way. These special locks have already been installed on windows at some off-campus housing.

The devices allow the windows to open to about three inches, which should prevent an attacker form getting in through an open window. CSU has ordered several dozen of these locks and will be installing them early next week.

Officials believe that the windows are probably the campus' greatest security threat, and that students are well-protected in other ways, 7NEWS reported.

"To get into the building, the student has to have a front entrance key and then to get into their room, they have to have a high security key," CSU Housing spokesman Dave McKelfesh said. "And then the buildings are all locked in the evening."

None of the five sexual assaults in Fort Collins have happened on campus, but four occurred just within a mile or two of CSU, 7NEWS reported.

The suspect's target seems to be young women in their early 20s, which is why there is a heightened sense of alert on campus.

Fort Collins police are also comparing notes with police in Boulder, where sexual assaults that took place three years ago have some similarities with the recent attacks.

In both cities, the suspect entered his victim's apartments through unlocked doors or windows, he blindfolded the women before the assault, and he smelled strongly of cigarettes.

But there are also differences. The Boulder victims were not able to give police a consistent description of the suspect, whereas in the Fort Collins assaults, the suspect was described as white man with a dark complexion, in his late 20s or early 30s. He was between 5-feet-9 and 5-feet-11 with a boxy torso, slightly overweight and had short to medium dark brown hair.

The Boulder attacks also happened in the late evening, not in the early morning like the attacks in Fort Collins.

A reward is being offered for tips that lead to solving these crimes. Anyone with information is asked to call Detective Kim Cochran of the Fort Collins Police Department at 970-224-6090.