(NewsNation Now) — A controversial COVID-19 testing chain is temporarily shutting down amid a federal investigation and mounting complaints.   

The Center for COVID Control, a national chain with more than 300 testing sites, is slated to shut down for one week, starting Friday.

“They are not responding to complaints at all,” said Steve Bernas, president of Chicago’s Better Business Bureau. He warned people about the pop-up testing sites affiliated with the Center for COVID Control.

“The majority of complaints allege that there’s no response after the taking of the test, there’s a payment required for expedited services, and they don’t get the expedited response,” Bernas added.

The BBB gave the Center for COVID Control an “F” rating. The Illinois Attorney General’s Office is investigating the company, which is not licensed or regulated by any government agency.   

The Massachusetts Department of Public Health on Thursday issued cease-and-desist orders to testing sites in Worcester, Needham and Dartmouth, all operated by the Center for COVID Control.

In response, Center for COVID Control CEO Aleya Siyaj said, “Regrettably, due to our rapid growth and the unprecedented recent demand for testing, we haven’t been able to meet all our commitments. We’ve made this difficult decision to temporarily pause all operations until we are confident that all collection sites are meeting our high standards for quality.” 

The company said the intense demand for testing during the omicron surge had strained staff members, leading to long wait times at test centers and delayed results.   

During the hiatus, the CEO said the company will hire additional staff, improve customer service, and make sure they can comply with regulatory guidelines for COVID testing.   

NewsNation affiliate WGN-TV and The Associated Press contributed to this report.