Drugstore chains CVS and Walgreens are expanding free coronavirus testing services.

CVS Health announced Monday that starting in May, it "will offer self-swab tests to individuals meeting Centers for Disease Control and Prevention criteria." The move comes in addition to large-scale testing the company has been offering at some locations in five states since March.

The new free self-swab testing will take place at up to 1,000 CVS locations by the end of May, which equals more than 1 in 10 of the company's stores.

Patients will schedule tests online and will get tested in CVS parking lots or drive-thru windows. The company won't conduct testing inside its stores.

The company said its goal is to process up to 1.5 million tests monthly.

Plastic shields, capes:How salons, gyms plan to re-open after coronavirus closures

No tax refund yet? Here's why the IRS might be giving you the cold shoulder

Separately, CVS rival Walgreens announced it's opening free drive-thru nasal-swab testing sites in 49 states and Puerto Rico. It was not immediately clear how many stores would offer tests, but the company said it expects to test more than 50,000 people weekly once it's fully operational.

Walgreens already has 18 drive-thru testing sites open in 11 states. Patients must make an appointment online and meet CDC criteria.

Walmart, which began opening free drive-thru testing sites in mid-March, plans to expand from 25 more sites this week and a total of more than 100 by the end of May. That will allow it to conduct 20,000 tests a week, the retailer says. So far, it has tested nearly 13,000 people.

Walgreens said it would "focus its efforts on improving access to testing in underserved communities, and over time will also be working with companies to provide testing to employees, to help more businesses reopen in the weeks and months ahead."

CVS also said it would place a special emphasis on improving "access to testing and necessary care for historically underserved communities," including boosting mobile testing options.

"Employees participating in the test collection process will maintain safety using personal protective equipment and follow sanitization protocols after each test," CVS said in a statement.

People who attempt to register for a test will be "asked a series of questions based on established CDC criteria for testing," CVS spokesman T.J. Crawford said in an email. "If you meet that criteria, you’ll be able to choose a time slot."

Grocery chain Kroger also said Monday that it would expand drive-thru coronavirus testing. The company will provide testing at 50 stores in more than 12 states with plans to conduct up to 100,000 tests by the end of May.

Follow USA TODAY reporter Nathan Bomey on Twitter @NathanBomey.