Responding to concerns about the safety of its funky resin shoes, Crocs Inc. said Monday it is introducing two models aimed at medical professionals that will come without the distinctive holes of its traditional styles.

The new shoes are made with the company's patented proprietary closed-cell resin and offer a thicker layer of protection for the top of the foot, Crocs said in a statement.

Concerns have been raised that doctors and nurses wearing Crocs could be injured if instruments or needles fell through the holes. Other worries have been raised about whether Crocs generate static electricity that can knock out medical equipment.

Crocs is based in Niwot north of Denver and its shoes are sold in more than 80 countries.

Its shares rose 24 cents to $58.15 a share in Monday morning trading.