A day after the Sandia National Laboratories in New Mexico had mostly reopened Building 823 after a case of COVID-19 among its workforce, the Department of Energy facility had to close down Building 720 after the disease caused by the novel coronavirus 2019 popped up there as well.

Building 720, which houses the Ion Beam Laboratory, will be closed down for a deep cleaning that typically takes about a day. In a statement posted online, Sandia said one person in Building 720 was infected. The lab now is performing contact tracing among that person’s coworkers.

Building 720 also shut down because of COVID-19 this spring.

Meanwhile, Building 823, which houses laboratories including for Sandia’s geosciences program, reopened Tuesday after someone there was confirmed to have COVID-19.

Sandia is able to test its own employees for the respiratory illness. The confirmed cases announced for Albuquerque this week will be on top of the 36 infections the the lab was tracking last week: 28 at Albuquerque, and eight at the lab’s the Livermore, Calif., satellite. That was up from 31 cases from the preceding week, with 24 in Albuquerque and seven in Livermore.

Sandia designs the non-nuclear parts of nuclear weapons — which the civilian Department of Energy’s National Nuclear Security Administration owns, maintains and modernizes — and tests the non-nuclear parts of existing weapons to make sure the U.S. arsenal is functioning as designed.

Further south in New Mexico, a seventh case of COVID-19 has been confirmed at DoE’s Waste Isolation Pilot Plant, the Carlsbad Current Argus reported this week. The agency is mining out further space in the deep-underground disposal site to accommodate nuclear waste that the Los Alamos National Laboratory will produce starting in the middle of this decade as a byproduct of casting plutonium cores for future intercontinental ballistic missile warheads.

Nuclear Waste Partnership, DoE’s management prime for the Carlsbad-area transuranic waste disposal facility, confirmed the case among its workforce. Contact tracing and sanitizing were underway, according to the contractor.

Three of the cases at WIPP have involved Nuclear Waste Partnership employees, according to the Current Argus. The other four have been employees of WIPP subcontractors.