URBANA, Ill. (CBS) — The University of Illinois at Urbana-Champaign on Wednesday warned the student body that irresponsible behavior has caused a number of COVID-19 cases within the undergraduate student body and is running the risk of jeopardizing in-person learning.

Students have been ordered to avoid social gatherings for the next two weeks and have been warned that there will be consequences for conduct that could spread the virus.

In a letter, U of I said students’ poor choices had led to a rapid increase in the number of positive COVID-19 cases, and said for two weeks – beginning now – the university will be “intensifying our efforts to identify and swiftly remove those individuals who have created this unacceptable risk for our campus and community and who have undermined your hard work to stay together.

“Students who continue to violate our safety policies, who fail to comply with directions from our public health officials and who engage in unsafe activities that risk spreading the virus will be asked to leave this university,” the letter said.

The university added that the damage done by the students who behaved irresponsibly can be reversed – but it must be done quickly and it will require action on the part of students.

With that in mind, for the next two weeks starting at 5 p.m. Wednesday, all undergraduate students will be expected to limit in-person interactions to “only the most essential activities” – such as taking twice-weekly COVID-19 tests as required for everyone on campus, attending class, buying groceries and food, going to work, engaging in individual outdoor activity, attending religious services, and seeking medical attention.

But social gatherings will be a no-go.

“We need you to strictly avoid social gatherings under any circumstances for these two weeks. We know what we are asking with this. Being together with friends is a big part of why you chose to come back. And for our freshmen, opening your college experience with the same isolation that ended your high school career is intensely disappointing,” the university said. “It is not fair that you will be the ones to fix a situation you did not cause. But this is where we are now, and this is what it will take to repair the damage in time to break the cycle of increasing new cases. Two weeks now gives you the chance for the rest of the semester together.”

The university said some students have ignored Champaign-Urbana Public Health District directives to isolate or quarantine even though they know they have tested positive for the coronavirus, and some students who have tested positive are avoiding contact tracers – or have repeatedly returned to testing facilities in an effort to “test out” of their positive status, which is not allowed.

Some students have also made active efforts to circumvent the Safer Illinois app, the university said.

Over the weekend, the university got 11 complaints about large gatherings at fraternities and private houses and more than 100 calls about parties.

The university has now identified more than 400 new positive cases since classes resumed on Monday, Aug. 24, and about twice as many people are now in quarantine.

The U of I also warned that there will be disciplinary consequences for students who take actions that could spread COVID-19 – and some students have already found themselves in trouble.

One student was issued an interim suspension for hosting a large party at his apartment on Friday, and another was issued an interim suspension for violating a quarantine order on Saturday. A student who posted a video on social media attempting to instruct people on how to circumvent the Safer Illinois app is also in trouble.

The Pi Kappa Phi fraternity has also been suspended after another large party this past weekend, and about 100 more students and organizations are also facing disciplinary action.

“These violations are unacceptable, and as we identify more individuals who are being irresponsible, they should be prepared to interrupt their studies and leave campus,” the letter said. “Students who do not comply with campus COVID-19 rules or who fail to follow any instructions from Champaign-Urbana Public Health District will face immediate suspension.”

The office of the Vice Chancellor of Student Affairs has increased staffing to keep a watch for large gatherings, parties, and other unacceptable activities. The university is also stepping up its contact tracing efforts, and those who do not comply with quarantine or isolation will face immediate suspension.

Anyone who does get a call from the Champaign-Urbana Public Health District, beginning with a 217 or 312 area code, must respond immediately and follow quarantine or isolation orders. Those who fail to do so are violating state law and will be suspended.

In addition to university disciplinary action, any student violating rules for COVID-19 mitigation could be fined $750 per day as per emergency orders from the cities of Urban and Champaign.

“We have created the most extensive testing process of any university in the country. We have extensively modeled to make the best science-driven decisions. We have invented a new COVID-19 test. We’ve created a new app to ensure building access and academic standing are linked to testing compliance. Seven teams have worked since the spring to do everything we could possibly think of to make your Illinois experience as normal as possible,” the university said. “We’ve given ourselves a real chance to come together and to stay together. But the decision to do so is in your hands. We stay together. Or we go home. It comes down to these next two weeks. It is up to you.”

Of the 2,557 positive cases in Champaign County, 782 are under age 20 and 744 are between the ages of 20 and 29. Thus, more than half are children or young adults.