A visitor to Principal Financial Group's downtown Des Moines office has tested positive for COVID-19, leading to nearly 20 floors of the skyscraper commonly known as 801 Grand to go through a "deep clean" that was scheduled to start Friday.

The visitor worked March 10-12 in Principal's office space, which includes floors 4 through 23. According to a notice sent to employees Thursday evening, all workers who were in the building during that time are being required to self-quarantine for at least 14 days starting with the day they were most recently in the office since March 10.

Employees who do not work at 801 Grand and haven't been to the building since March 10 are not expected to self-quarantine. The notice also told unaffected workers that if they haven't been working from home, but want to as a precaution, to work with their team leaders.

"We'll do all we can to accommodate remote working options," the notice reads.

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Principal spokesperson Jane Slusark said in an emailed statement that the company learned of the incident on Thursday. In addition to employees, Principal alerted other tenants of the building.

"A majority of Principal employees in Des Moines are already working remote and we have significantly limited visitors to our campus," the statement reads. "Our top priority remains protecting our employees and their families, while continuing to serve our customers.”

The 44-story building is owned by Principal. The retirement services company has more than 10,000 employees in the United States and is one of central Iowa's largest employers, with some 6,500 workers in the Des Moines metro area as of January 2019.

Slusarak did not immediately return a message asking for the number of employees who may have to enter into self-quarantine as a result of the visitor, or how long Principal's floors may be affected by the deep clean. In response to questions about the effect the exposure might have on other tenants at the building, the building's property manager directed inquiries to Principal public relations.

Correction: An earlier web headline on this story stated the building would be closed. About 20 floors that may have been exposed will undergo a deep cleaning, but the building is expected to remain open.

Nick Coltrain is a politics and data reporter for the Register. Reach him at ncoltrain@registermedia.com or at 515-284-8361. Your subscription makes work like this possible. Subscribe today at DesMoinesRegister.com/Deal.