LEWISTON — The outbreak of COVID-19 at Bates College is growing ever more dire.

Results from campus-wide testing on Monday found another 28 students infected with the coronavirus, pushing the tally overall to 77 students with active cases.

Those students have been moved into isolation housing, which means that dormitory space that had been empty two weeks ago is now more than two-thirds full. It has 113 units.

A graph showing the increased use of isolation housing at Bates College during the past two weeks as COVID-19 cases have soared. Bates College

There are 106 students in quarantine because they were in close contact with someone who has COVID-19 — down from 134 on Monday — an indication that at least a couple of dozen students who had been quarantined wound up testing positive and have been moved to isolation housing.

The outbreak began on March 25, when 45 students were found to have caught the potentially deadly disease.

Bates ordered a lockdown last Thursday to try to thwart further spread of the disease, requiring students to stay in their rooms except for limited circumstances. Initially set to expire Sunday, the college has already extended the edict through at least next weekend.

Students are each tested three times a week, with both rapid tests and more accurate ones that are processed at the Broad Institute in Boston. Any student who tests positive either way is immediately put into isolation housing.

College administrators blame the outbreak on three parties, two on-campus and one off, that occurred on March 26 and March 27. But they also say students had grown too lax in following rules that require social distancing and wearing masks.

During the entire fall semester, 25 Bates students caught COVID-19. So far this semester, there have been 106 cases among its 1,800 students.

Bates employees have fared better. This semester, the college has had five cases among its faculty and staff, only one of them still active.