A Richmond, California, day spa is permanently closed after two people died of Legionnaires’ Disease, contracted in its hot tub.

Zen Day Spa, located about 20 minutes north of San Francisco, shut its doors this August after area hospitals reported the deaths of two people who had visited the business before becoming ill.

The Contra Costa Health Department (CCH) began investigating the spa on August 4 after the deaths were reported on August 3rd and 4th. The business voluntarily closed on August 5 and remained closed under a health order issued by CCH while officials awaited final reports from a lab. Initial results showed high concentrations of legionella bacteria in the hot tub.

As part of its investigation, CCH contacted more than 30 recent customers of Zen Day Spa as well as recent cases of Legionnaires’ Disease reported through community healthcare providers. Health officials said they were looking through the business’s credit card receipts and appointment books to track down customers that might have been infected.

Beyond the two people who died with lab-confirmed Legionnaires’ Disease, as of August 21, CCH has identified two other people who visited the business and had labconfirmed Legionnaires’ Disease, and two people who reported becoming ill after visiting the business, whom investigators suspect had Legionnaires’ Disease.

In a press conference, Kim McCarl, with Contra Costa Health, said that Legionnaires’ Disease is contracted when aerosolized water is infected with the bacteria.

“So that is what happened in here,” McCarl said. “A closed room with water that is vaporizing. There is a waterfall that comes out of the hot tub, so obviously there was a lot of steam. And so, that is why the risk here was so great.”

Meanwhile, it is uncertain if the business was fully permitted to operate. John Gioia, Chair of the Contra Costa County Board of Supervisors, explained that there are two types of permits that a business such as Zen Day Spa is supposed to have: One is an environmental health permit to operate the hot tub, and the other is a city permit.

“The city is checking into whether they had a city permit or not — we don’t know that yet,” Gioia said. “We just know that there was no environmental permit.”

McCarl said that because the spa did not have the environmental permit, they were not on the health department’s inspection radar and were thus never inspected as per regulation. “Our staff is going to take a look and see if they ever were permitted,” McCarl said.

Officials are also looking into whether the business was acting with disregard for obvious risks to human life and safety. “Whether or not there was any criminal negligence, that is up to the district attorney.” Gioia said. “But this is also the kind of matter where we would also ask our district attorney, Diana Becton, to look at.”