University officials said someone in Watterson Towers hung clothing on a sprinkler line Tuesday night.
It triggered the fire alarm to go off and water to soak several student rooms on the 11 floors of the north tower.
Students had to be evacuated, some for as long as four hours. Others were let back in after about 20 minutes.
Another evacuation took place Wednesday because water caused the alarm system to malfunction, officials said.
"We woke up at around nine to the fire alarm going off so we grabbed our stuff and went outside, and everybody else was already out here," said student Sarah Southall.
Alli Macha said, "I feel very lucky that it wasn't me, but I'm hoping they get their stuff back and that things aren't too damaged."
The extent of the damage appears to be isolated to floors and carpet, but officials said they are in the process of cleaning it up.
Any student who needs something replaced can turn a receipt in to the university, but restitution is not a guarantee.
Officials said the Normal Fire Department is investigating to determine if the sprinkler was deliberately tampered with.