VANCOUVER -- Customers at two supermarket chains in Canada will soon have to wear face coverings while shopping.

In an online advisory posted earlier this week, T&T Supermarket said masks must be worn as of May 11.

Describing the pandemic as a "critical time," the grocery store chain cited Public Health Agency of Canada advise that appropriate use of face masks or coverings can reduce the spread of COVID-19.

And in an email to CTV News Thursday, Whole Foods Market confirmed its stores would implement a similar policy.

"In addition to requiring everyone working in our stores to wear face masks, over the next week we will begin requesting that all customers wear masks while shopping in our stores," a spokesperson said in part.

"Whole Foods Market will be providing face masks at the entrance of all stores for customers who do not have their own face coverings."

At least one store in Vancouver already had the policy in place on Thursday.

Health Canada has said non-medical face masks can reduce the spread of the wearer's own infectious respiratory droplets.

Non-medical face masks or other face coverings should fit securely to the head with ties or ear loops, maintain their shape after washing and drying, be changed as soon as possible when damp or dirty, and be made of at least two layers of tightly-woven fabric.

Read more on appropriate use of masks from federal health officials. 

Both stores said the policy is meant to protect staff, as well as other shoppers.

T&T is not handing out masks, but asked those without access to a face covering to shop online instead.

Last month, T&T was the first Canadian grocery store chain to test customers for fever before they entered.

At a location in downtown Vancouver, a security guard stood outside the front door, armed with an infrared thermometer which could be used to get temperature readings from customers' foreheads.

The screening is mandatory for staff, but still an option for customers.

Health officials including B.C.'s provincial health officer raised doubts as to whether the measure would be useful in detecting cases.

"Not having a fever doesn't mean that you're necessarily safe," she said at the time.

"You can have other symptoms that might be indicative of being sick."

May 13 update: In an email to CTV News Vancouver, T&T Supermarket said it will now be providing masks for shoppers who don't have one. They will be charged $1 for the mask, at checkout, and the company says any proceeds from the sale of those masks will go to the President's Choice Children's Charity.