A new report says Kay Jewelers, a diamond ring chain used by many for engagement and wedding rings, not only has lost some customers' jewelry, but may have deliberately swapped diamonds for lower-quality stones.

The latest investigation by BuzzFeed found several Kay Jewelers customers who took in their engagement rings for repair or an inspection discovered the diamond in the rings had been swapped. In one case, the stone in the ring tested as moissanite, a more affordable and inferior stone.

Kay Jewelers told BuzzFeed they are looking into the complaints, but that the company has a stringent policy in place to make sure stone swapping doesn't occur, because there is a certification number on each diamond. In some of the cases that BuzzFeed uncovered, the certification numbers did not match.

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In an earlier report, BuzzFeed News reported that Kay Jewelers customers had taken to social media to complain about issues they had with the company.

Nicole Largent paid extra for an extended service plan for the ring she and her husband Josh got from Kay.

The service plan allows customers to have certain repairs and maintenance done on their ring "up to the amount of the purchase price, at no additional charge," as long as they keep up with maintenance inspections every six months.

Largent said she and her husband brought the ring to a Kay in Hagerstown, West Virginia, and were told by an employee that the ring was loose and needed to be fixed.

Largent said the ring was sent to Jared, a chain that is owned by Kay, and when she called to ask about picking up the ring, she was told it was lost.

“It’s really devastating, because we could get a new ring, you can get new jewelry, but you can’t get back your original,” she said.

Complaints also populate Kay's Facebook page, saying that rings sent in to be fixed are often returned in worse condition.

Makenzie Balderson took her ring to a Richmond, Virginia, Kay to be resized and to fix a crooked diamond.

“I basically just had to hand them the ring I just got engaged with a week prior, and I never got to see that ring again,” Balderson said, explaining to BuzzFeed News that Kay told her the ring was defective and had to be "damaged out."

She said the replacement was worse.

"The center diamond is still crooked, there is proof on my ring that it was sized and wasn't actually casted for my size and I have black dots on my ring from them working on it, as well as a missing stone," she wrote in a Facebook review.

Balderson ended up getting a new ring from a different company.

Ashley Brown said her local Ringwood, New Jersey, Kay told her she would need to order a new ring to when she needed her ring resized. When she picked up her new ring, she saw a "drastic difference in the look of the ring."

Although employees originally asked her if the rings were the same, Brown told BuzzFeed News they suddenly told her the rings had the same quality, so she kept the new ring and left.

“When I got back home I showed everyone and they were all shocked at the difference and said I was right and needed to go back and get my old ring,” Brown said she ended up going back to Kay and was able to exchange her ring and keep her old one.

Kay spokeswoman Kimberly Kanary said in a statement to BuzzFeed News:

"We take this matter very seriously and are currently working with the authorities on responsibility and recovery. As this is an ongoing investigation, we are unable to comment further to this end.

"We are continuing to work diligently with the guest on this matter. We have provided options that we are confident reflect commensurate value, and we are committed to collaborating with the guest on a satisfactory resolution."

Kay's Lifetime Diamond and Color Gemstone Guarantee says it will "replace, free of charge, any diamond, emerald, ruby or sapphire covered by this guarantee if it chips, breaks, or is lost from its original setting during normal wear," provided the six month inspections are kept.

Since the report emerged, more customers have complained on the Kay Facebook page about problems with earrings and other engagement rings.