Shares of leading generic drugmakers plummeted Thursday following a report that US antitrust investigators could unveil criminal charges of price-fixing by the industry before year-end.

The Department of Justice is probing whether executives from different companies colluded on drug prices, said a Bloomberg News report, citing unnamed people familiar with the probe.

The probe covers more than a dozen companies and about two dozen drugs, Bloomberg said. 

Shares of several of the companies named in the article fell sharply including Mylan, down 7.0 percent, Teva, down 10.9 percent, Endo International, down 17.3 percent and Impax Laboratories, down 13.4 percent.

The investigation represents another cloud hanging over the pharmaceutical industry, which has been battered by criticism over runaway drug prices.

Mylan, in particular, has been under fire for hiking the price of its EpiPen allergy medication from $100 in 2007 to more than $600 for a two-pack.

Bloomberg said the probe may resemble a Department of Justice crackdown on the auto parts industry dating back more than a decade, which resulted in $2.8 billion in fines and charges against 46 companies.

Charges in the generics price-fixing case could come in December, although the timing could lapse, the article said.