PORTLAND — The makers of Chobani yogurt instituted a voluntary recall Thursday after customer complaints led to the discovery that some yogurt containers, including units sold in Maine stores, were contaminated with mold.

However, the company did not inform some stores in time to withdraw all the affected containers before some were sold.

Chobani, the second-best-selling Greek yogurt brand in the U.S., last week began contacting individual retailers about the problem and asked them to remove yogurts stamped with the lot number 16-012 with expiration dates between Sept. 11 and Oct. 7. At the time, the company called the procedure a “voluntary withdrawal,” but on Thursday morning changed that to a voluntary recall.

The yogurt still was being sold in some Shaw’s stores, including stores in Maine, as late as Wednesday night, even though Chobani began informing stores about affected products last week.

Steven Sylven, a spokesman for the Massachusetts-based Shaw’s chain, said Chobani told the company last week that the yogurt it was selling wasn’t affected by the mold. But on Wednesday night, he said, Chobani said that initial information was wrong and Shaw’s had some of the affected products.

Sylven said Shaw’s immediately ordered stores to remove the product from shelves. Sylven said he did not know how many containers of yogurt had been sold before stores yanked them from shelves or how many were removed.

Hannaford Bros. spokesman Mike Norton said Chobani asked them to remove yogurt “flips” — products that come with the yogurt and fruit or nuts in separate containers — and 3.5-ounce yogurt “bites” from store shelves. The supermarket chain pulled 9,100 packages in 182 stores from the shelves Friday and Saturday, he said.

Hannaford plans to throw away the affected yogurt and receive a refund from Chobani. Norton declined to specify the amount of the refund.

Whole Foods in Portland said it was notified about the yogurt last week, but the lot numbers of the yogurt in its inventory did not match the ones the company identified as potentially contaminated with mold.

Customers have said the affected yogurt made the containers swell up and produced an “off” taste that some described as “fizzy” and others said tasted like wine. Some reported the yogurt made them sick.

Late Thursday afternoon, Chobani posted an apology from company founder Hamdi Ulukaya on its website, which was unavailable part of the day and ran slowly when it could be accessed.

Information on the recall was included in a company blog. Customers had to click through several pages to find it, and the page where the information was posted was topped with a huge picture of a yogurt “cheesecake” treat. Readers need to scroll farther down the page to see the brief recall updates.

Chobani said the mold is “common in the dairy environment” but did not explain how it got into a batch of yogurt undetected, other than to say the company doesn’t use artificial preservatives.

The company also did not say what kind of health problems the mold might cause or even how many units of the yogurt were being recalled. Chobani said some customers did say the yogurt made them sick but did not say how many people were sickened, beyond saying it was not in the hundreds or thousands.

The company did not respond Thursday to requests for additional information.

The federal Food and Drug Administration is talking with the company about the recall and whether the company had communicated with the public appropriately, but a spokeswoman would not give details.

Customers are advised to go to chobani.com/care to seek a refund or replacement if they bought yogurt from the affected batch.