The University of Maine System is expanding its testing plans for the fall after reporting a fourth case of COVID-19 on Monday as colleges around Maine began welcoming students back to campus.

In addition to the three students who tested positive last week at the University of Maine in Orono, a student at the University of Maine School of Law in Portland returning from out of state also has tested positive.

The system said it is expanding its three-phase testing program to include random testing of asymptomatic individuals across the system in the third phase, which follows two rounds of testing for select groups of students upon arrival on campus and again shortly after the start of classes on Aug. 31.

“Student and community health is our top priority,” UMaine System Chancellor Dan Malloy said in a statement. “Our Scientific Advisory Board has developed a sampling strategy for asymptomatic individuals that will give us actionable, up-to-date information throughout the semester about our efforts to limit the spread of infection and to protect our students, employees and communities.”

Also on Monday, Colby College in Waterville notified the community it has had five positive tests – three among students and two among staff – over the past month. Colby has conducted more than 6,400 tests including 4,700 on campus and 1,700 before students started arriving on campus last week. The college enrolls about 2,000 students. In-person classes are scheduled to start Wednesday.

In an email to the community Monday night, Karlene Burrell-McRae, dean of the college, said the two employees who tested positive were retested and received two consecutive negative results. One had been working remotely since March and the other was tested early in the process and has since left the college for a position elsewhere.

The three students who tested positive are not experiencing symptoms and are in isolation. Their cases are unrelated and were not contracted at Colby, Burrell-McRae said.

“Our testing program is functioning as we intended: first, it is helping us to identify anyone who might be infected and therefore at risk and/or potentially putting others at risk; second, it is setting the baseline for future testing,” Burrell-McRae said. “This is important because the test Colby is using is a highly sensitive PCR test that can detect evidence of the virus in a person’s system long after the individual is contagious.

“We believe we have seen this already with some of our positive cases – individuals had evidence of the virus in their bodies, but it is highly probable that they contracted it some time ago and have passed the period of contagion. Identifying those cases now allows us to launch the academic year with a full understanding of the health of our community.”

In each of the positive cases detected at Colby in the past several days, contact tracers identified and contacted individuals who needed to quarantine based on CDC guidelines. The test-positive individuals were immediately isolated and retested as quickly as possible. In some cases, additional tests returned negative results, Burrell-McRae said.

The college has launched an online dashboard to include negative tests, inconclusive tests and positive cases, including those in isolation as well as information on Colby’s health code.

“We knew that when we began testing we would identify positive cases, and Colby has developed an effective process for using testing to protect our community and care for test-positive individuals,” Burrell-McRae said. “While in many ways this news is encouraging given the number of tests we have conducted, we need to recognize that the virus is around us.”

The return of students to Maine campuses comes as colleges and universities around the country are struggling to control outbreaks and enforce limits on mass gatherings.

Some schools, such as the University of Notre Dame and University of North Carolina at Chapel Hill, have had to backtrack on reopening plans and move classes online because of outbreaks on campus. Other schools, such as Syracuse University and Penn State, have disciplined students for failing to follow physical distancing guidelines.

Testing protocols on campuses vary. Bates College in Lewiston will begin welcoming students back in earnest Tuesday and plans to test all students upon arrival, then again three days later and then twice weekly throughout the semester, including students who live off-campus but are taking classes in-person.

Faculty and staff with frequent close interactions with colleagues and students are being asked to test twice per week while other employees who are frequently on campus but have more limited interactions are encouraged to test once per week.

The college also has launched a dashboard to keep the public informed of test results. As of Monday the dashboard was showing no positive results among the 94 students and 574 employees tested. Bates enrolls about 2,000 students and has about 800 employees, though some will work remotely this fall.

Sarah Delage, a spokeswoman for the University of New England, said all undergraduate students are required to present a negative test upon arrival on campus and then they are immediately tested again. As of Sunday the university had tested 865 students and all tests were negative. Move-in is still underway and preliminary data on all undergraduates should be available later in the week, Delage said.

She said the university intends to report cases on its website and will be communicating the process to faculty, staff and students this week.

At UMaine, the law student was tested at a venue not associated with the university’s testing program and received the results before any contact with Maine Law students, faculty or staff. The student is now in isolation and doing well with support from the law school, the university said.

The state system said Monday it will expand its testing program to include asymptomatic testing of approximately 2,000 students, staff and faculty members systemwide at least every 10 days through the Thanksgiving holiday, which marks the end of in-person instruction for the semester. The 2,000 individuals represent about 10 percent of the students and employees the system expects to be engaged in in-person activities this fall.

All community members who work, study or participate in on-campus activities will be subject to the random sampling to monitor and limit the spread of COVID-19.

In addition, the university is moving ahead with its plans to test all residence hall and out-of-state students and special populations, such as student athletes and students participating in off-campus clinical experiences, upon the return to campus and again shortly after classes begin.

Phases one and two of the testing program involve approximately 12,500 individual tests in each phase, making the university system one of the region’s largest asymptomatic test providers through a partnership with Jackson Laboratory and ConvenientMD. The three-phase program is budgeted at about $6 million and testing is being offered at no cost to students or employees.

The number of tests to be conducted in phase three will be determined by an analysis of the incidence rates in phases one and two and statistical modeling employed by university scientists.

The UMaine System also has launched a testing dashboard that showed 1,372 tests had been done across the system as of Monday with one positive test result. The data does not include results of tests done at outside venues, such as an individual’s doctor’s office or a hospital.