LOS ALAMITOS (CBSLA) — A second student at Los Alamitos High School has tested positive for COVID-19, just two weeks after the campus reopened to in-person learning.

The school’s principal sent a letter to parents of students who might have been exposed, informing of the second positive test, just a few days after notifying them about the first COVID-19 infection.

Los Alamitos High School reopened two weeks ago for in-person learning, one of the first public high schools in Orange County to have students return back to campus. Orange County is in the state’s red tier, which allowed more businesses to reopen their indoor operations and schools to reopen for in-person learning.

The infected students and those who came in close contact with them are now self-isolating for 14 days.