Boston Scientific

(BSX) - Get Report

tanked Thursday afternoon after the medical device company added 3,000 more stents to a recall that was first implemented July 2.

The expansion of the recall is another black eye for the Natick, Mass., company, which had previously seen hospitals slowly resume use of its Taxus stents after it recalled about 86,000 of them in mid-July. The devices, which are used to prop open arteries after they are unclogged in balloon angioplasty, have been found in rare instances to impede deflation in the procedure.

"The company reiterated that patients who have already received stents are not at risk, because any difficulty associated with non-deflation occurs during the implantation procedure," Boston Scientific said Thursday. The company added that since it modified its manufacturing process and took other actions, it has confirmed zero no-deflate complaints in nonrecalled units.

The stock was nevertheless down $3.11, or 8.6%, to $33.20, leaving it off 23% since the start of July.