Twenty-eight University of Texas students who returned to Austin from a spring break trip to Cabo San Lucas, Mexico, have tested positive for the coronavirus, UT officials say. Dozens more are being monitored.

Austin Public Health officials said Tuesday a group of about 70 people in their 20s took a chartered plane to and from Mexico about 10 days ago. Some flew back on commercial flights. Four of those who tested positive showed no symptoms. In addition to the 28 who tested positive, a university spokesman said it is believed many in the larger group were UT students.

Austin Public Health, UT Health Austin and University Health Services have made contact with every spring breaker on board the charter plane and are in the process of tracing the commercial flights’ other passengers. The 28 confirmed cases are self-isolating, and others are under quarantine while being monitored and tested, Austin Public Health said.

UT spokesman J.B. Bird said the college is working closely with Austin Public Health to assist in contact tracing.

In total, UT says it is aware of 38 students and seven faculty members who have tested positive for coronavirus, are presumed positive or self-reported.

Local health officials said Mexico was not under a federal travel advisory at the time of their travel, but again urged Austin and Travis County residents to avoid all nonessential travel.

It appears many of the UT students were traveling to Cabo San Lucas with a company called JusCollege, which specializes in organizing trips for college students. In the weeks and days leading to spring break, the company sent multiple emails to UT students, saying there was no danger from COVID-19 and the refund policy on the trip packages — which students say were about $2,000 — remained nonrefundable.

"We’re currently in our 2nd week of Cabo and have had almost 5000 travelers, all with no issues," the company said to a UT student in March 12 email obtained by the American-Statesman. "Flights have been fully operational and we have had nearly 100% turn out. Our events are completely operational with zero impact from COVID-19 thus far."

The company did not respond to requests for comment. A March 25 announcement, however, said the company has postponed spring break trips and is working on credits or partial refunds for those who can’t attend the new trip dates.

Alberto and Stacy Saenz were celebrating their first wedding anniversary in Cabo San Lucas in mid-March, which overlapped the time the students were there.

Alberto Saenz said news of the positive tests originating from Cabo were concerning. Both he and Stacy are asymptomatic, but they want to do the right thing and make absolutely sure they don’t spread the virus to others. However, he could not obtain information about which flights students returned on from Austin Public Health, nor had he heard anything from the airline, he said.

"If in fact we were on one of those flights, that’s a break in communication right there if we haven't been told," he said.

Austin-Travis County Interim Health Authority Dr. Mark Escott said COVID-19 hides in the healthy, from whom it is transmitted to vulnerable people more susceptible to deadly complications. However, there still is risk for young, healthy people.

Nearly half of those who have tested positive for COVID-19 are between 20 and 40 years old, city and county records show.