SAN JOSE, Calif. — An employee at Kaiser Permanente in San Jose has died after they and dozens of colleagues contracted COVID-19. Officials are investigating the possibility the infections may have come from a Christmas costume.

Kaiser says 44 staff members in the hospital’s emergency department tested positive for COVID-19 between December 27 and January 1. The facility was investigating the outbreak and told KGO the spread “may” have been connected to an “air-powered costume.”

The blow-up holiday costume, reportedly a giant Christmas tree, was worn by a staffer who “briefly” visited the emergency department on December 25, according to KNTV.

Inflatable costumes usually rely on battery-operated fans to suck air into the costume to keep its shape. COVID-19 spreads through droplets in the air, which is why investigators are looking into the air circulation function of the fan.

Kaiser says the costume was not approved beforehand by the hospital.

The person who died has been identified by San Francisco media as a registration clerk in the emergency department of the hospital.