The reward for information leading to an arrest and conviction in the threatening notes found at Highland Park High School has been raised to $10,000.
The school has been forced to increase security at the campus after six security scares were reported in less than two months.
Metal detectors will be available for authorities to search students at the high school. All students will have to carry their identification with them and will see an increased presence from police.
The FBI said it may start fingerprinting students to find any matches to the multiple threatening notes left at the school since Jan. 17. Meanwhile, the bureau is testing the bullets found Wednesday for DNA in an attempt to trace from where they came.
Highland Park Principal Walter Kelly said investigators were making progress in the investigation.
Kristin Johnson, whose daughter attends Highland Park, said the threats have stressed the community.
"Tuesday was kind of joking, laughable -- another go-around of pranks," she said. "And then Wednesday was a little more 'now I'm getting annoyed and it's a little scary.'"
Johnson said news of the threats has filtered down the middle school her two sons attend.
"My youngest called me from school and said, 'I heard they had bullets,' so I said, 'Emily is OK; calm down,'" she said. "You know, it affects the whole community."
So far, no arrests have been made in connection with any of the threats. Officials said if the threats are connected, the person responsible will face felony charges.
A $10,000 reward is being offered for information that leads to an arrest in the case.
The money is a combination of $5,000 from CrimeStoppers and $5,000 from the school district and parent donors. Anyone wishing to contribute to the fund may do so by emailing Tim Turner, assistant superintendent for business services, at firstname.lastname@example.org.
Anyone with information may submit a tip online or by calling 877-373-TIPS. The school is also providing a way for students to give anonymous tips.
Sixth Incident Since January
In what has become a recurring event, a threatening note was found at the high school on Thursday -- this time in a stairwell.
On Wednesday, students were again dismissed early after several .22-caliber bullets were found in a different boys bathroom.
With restroom access now restricted, the written bomb threat found Thursday was located in a stairwell.
Police said the note was very similar in writing and content to the ones found in the bathroom.
The school said in a note to parents Thursday that they did not believe the threat is credible and that students would not be dismissed early.
The Highland Park school district said Thursday that it plans to continue to have an added police presence until it feels it is no longer needed. The district also said it was looking at adding security wands.
"I'm not ready to make that call yet," Superintendent Dawson Orr said. "That does fundamentally change the nature of how kids enter into school every day. Right now, we [have] a very heavy police presence. We think the wands would be a backup -- it's something we do need to evaluate."
NBC 5's Frank Heinz, Kendra Lyn, Omar Villafranca and Ray Villeda contributed to this report.