The Royal Newfoundland Constabulary is asking for anyone who purchased foldable credit card knives on a local classifieds website to turn them over to police.

The RNC learned of a man in the St. John's area who was selling the knives on NL Classifieds, after it was flagged by members of the National Weapons Enforcement Support Team.

Police tracked the man down, and learned he bought 100 credit card knives online. He has since sold 51 of them. The RNC seized 49 of the knives.

Police warn that credit card knives are considered a prohibited weapon. (Royal Newfoundland Constabulary)

On Thursday morning, police located a second person who was selling the knives online. Credit card knives are considered prohibited weapons.

During that seizure, 30 knives were taken.

Anyone caught with one of the knives could be charged with carrying a prohibited weapon, as it's concealed with a blade less than 30 centimetres.

In a news release issued on Thursday afternoon, police assured nobody would be charged if they surrender the knives to RNC headquarters.