The Los Alamos National Laboratory is set to begin testing its own employees for COVID-19 on Tuesday, a spokesperson for the northern New Mexico lab confirmed Monday.

The local Los Alamos Reporter broke the news Monday.

Los Alamos is the second National Nuclear Security Administration (NNSA) nuclear weapons lab to begin testing; Sandia National Laboratories in Albuquerque and California was the first to begin tests for on-site personnel who are reporting to work to continue essential national security projects.

As at Sandia, Los Alamos tests will be by appointment only, and done at a drive-through, according to the lab spokesperson. The lab plans to first test personnel “working on-site in mission critical functions, medical professionals and emergency response personnel,” according to a statement provided Monday evening.

Los Alamos workers involved with mission-critical construction were among the four site employees who have so far tested positive for COVID-19, the independent federal Defense Nuclear Facilities Safety Board wrote in a report published Friday.

Los Alamos employs some 12,700 employees and contractors, most of whom are still working off-site. The nation’s first nuclear weapons lab is in the middle of a drive to upgrade its PF-4 Plutonium Facility to make pits, or nuclear cores, for W87-1 warheads slated for use on future Ground Based Strategic Deterrent intercontinental ballistic missiles.

“Following a successful pilot program and dependent on an adequate supply test materials, the Laboratory plans to expand the program to increasing numbers of high priority, on-site mission critical Laboratory and NNSA Federal employees,” Los alamos wrote in Monday’s statement. “Test collection will be through nasal or throat swab to detect viral RNA using a reverse transcription polymerase chain reaction (RT-PCR) test, not a blood antibody test.”

It was not immediately clear whether Los Alamos personnel would collect nasal swabs from employees, or whether the lab would contract that service out, as Sandia did. Either way, Los Alamos will process the tests on site in its new Covid-19 Diagnostic Testing Lab, the lab said Monday. The lab will report test results immediately to the New Mexico Health Department.