The Gemological Institute of America has banned more dealers in its ongoing probe into bribery allegations.

GIA has told the Wall Street Journal that it “has banned an additional group of dealers from having their stones graded.” The Carlsbad, Calif.-based organization continues its practice of refusing to name the dealers it has excluded for allegedly bribing GIA staffers. However, the WSJ, quoting “sources familiar with the investigation,” that at least three prominent dealers were among those banned in recent weeks.

“We felt there was enough evidence of unethical conduct to prompt us to send out another letter,” Kathryn Kimmel, a GIA spokeswomen told the WSJ. “We are trying to pursue all credible leads.”

GIA also told the WSJ that “numerous consumers” has taken up its offer to regrade stones for free.

JCK