AUSTIN (KXAN) — Austin Public Health is investigating a large group of people with a cluster of positive COVID-19 cases returning from a Spring Break trip to Mexico, the agency said Tuesday.

APH says about a week-and-a-half ago, the group comprised of approximately 70 adults in their 20s left for a spring break trip to Cabo San Lucas, Mexico on a chartered plane. Not all of those people came back on the same flight and some took commercial airlines back.

On Wednesday, the University of Texas at Austin confirmed 44 students have tested positive for COVID-19. It previously said Tuesday that 28 of the 70 had tested positive for COVID-19, and more of them are under public health investigation.

APH says UT Health Austin and University Health Services have made contact with every person on the trip, and all 28 people who tested positive for COVID-19 are self-isolating. Others are under quarantine while being monitored and tested, APH says.

When this trip happened APH said there was not a federal travel advisory to Mexico. However, Austin -Travis County residents were being advised to follow the U.S. Centers for Disease Control & Prevention recommendations to avoid all nonessential international travel. APH made it clear that this trip did not fall into the category of “essential travel.”

A city spokesperson explained that because this case is an active investigation, they can’t confirm whether these spring breakers are still in Austin now.

But UT Austin tells KXAN that because classes have now switched online at the university since March 30, almost all UT students have returned to their homes in Texas and around the world. This means these students, if they contract the virus, may report their case to the local health departments.

The University is working with Austin Public Health to determine all the individuals these students may have been in contact with.

UT Austin’s  Spring break was supposed to go from March 16- 21st. But then the University, like many other schools, decided to extend spring break. So classes just started back up on March 30 in an online format due to COVID-19.

UT told students to take preventative measures and to be cautious while traveling over spring break.

“The virus often hides in the healthy and is given to those who are at grave risk of being hospitalized or dying,” APH Interim Health Authority Dr. Mark Escott said.

“While younger people have less risk for complications, they are not immune from severe illness and death from COVID-19,” he said.

Data from the regional health authority shows that almost half of the people who have tested positive for COVID-19 in Austin-Travis County are between the ages 20-40, APH says.

“The incident is a reminder of the vital importance of taking seriously the warnings of public health authorities on the risks of becoming infected with COVID-19 and spreading it to others,” UT spokesman JB Bird said in a statement.

Bird tells KXAN that as of March 31 that UT is aware of 7 employees and 38 students in the UT Austin community who have tested positive for COVID-19 or are presumed positive.

KXAN Graphic based on Austin Public Health numbers. (KXAN Graphic/ Andy Davis).