An Amazon.com Inc. warehouse visited this week by chief executive officer Jeff Bezos confirmed its first employee coronavirus case, according to a message sent to workers on Thursday.

The employee who tested positive for COVID-19 was last at the site on Monday, according to the update Amazon sent.

“Consistent with our daily processes, the site has undergone enhanced cleanings since the associate’s last day,” said the message, which was reviewed by Bloomberg.

Amazon declined to comment.

Bezos made a surprise visit Wednesday to the warehouse, called FTW6, which is just north of DFW International Airport. It’s among more than 100 similar sites around the U.S. where employees are toiling to meet a surge in online orders from customers sheltering at home.

Today's visits by our founder and CEO @JeffBezos to say thank you to Amazon fulfillment center and Whole Foods employees. We're all incredibly proud of the thousands of our colleagues working on the front lines to get critical goods to people everywhere during this crisis. pic.twitter.com/dygb345wDM — Amazon News (@amazonnews) April 9, 2020

Bezos walked through the facility wearing a face mask, waving to workers and flashing thumbs up. He also visited a Whole Foods location, and Amazon posted video of his tours on Twitter.

The FTW6 warehouse has been cleaned multiple times since the infected worker was last in the facility, according to a person familiar with the matter who asked not to be identified because they’re not authorized to discuss the details.

Whole Foods Market, which has 14 North Texas stores and warehouses, has also reported that one employee tested positive and is in quarantine, according to a Dallas Morning News survey of grocery chains. The store underwent an additional deep cleaning and disinfection, the company said.

Related: The News went inside FTW6 in December 2018 to see how robots and humans fulfill Amazon customers’ holiday gift purchases.