An employee of a tenant at Chase Tower in downtown Dallas tested positive for coronavirus, Fortis Property Group announced in an email late Monday obtained by The Dallas Morning News.

In the letter to office tenants, the landlord wrote: “We believe the following incident has been contained and does not require further action.”

According to the email, the employee began feeling ill March 5 and has not returned to the 55-story office tower.

Before March 5, the building had begun receiving more comprehensive cleanings during the day and evening to disinfect common areas throughout the building, the email said.

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“As a result, the building has been disinfected each day and evening throughout this period,” the property company said. “The tenant also has been conducting extensive, ongoing cleaning and it is now performing a thorough deep cleaning of its space.”

Health officials have stressed the importance of washing hands and deep cleaning high-touch surfaces such as door handles and cellphones. It’s believed that the virus, which causes COVID-19, can last on a surface for up to three days.

On Monday, Dallas County banned gatherings of groups larger than 50, restricted restaurants to dine-out orders and implemented other sweeping social distancing measures.

Chase, the skyscraper’s major tenant, said it had already encouraged employees in Dallas and nationally to work from home if possible. It has about 600 workers in the downtown Dallas location.

Other tenants include some of the city’s most prestigious law firms, including Locke Lord LLP and Norton Rose Fulbright, as well as accounting and tax firm Deloitte and Cornerstone Healthcare Group.