Four female weightlifters from the 2012 London Olympics have been stripped of their medals after additional tests revealed they had banned substances in their systems at the time of competition. The International Olympic Committee made the announcement on Thursday. Kazakhstan’s Zulfiya Chinshanlo, Maiya Maneza and Svetlana Podobedova were stripped of their gold medals won in the 53-kilogram, 63-kilogram and 75-kilogram competitions, respectively, and Belarus’s Marina Shkermankova was stripped of the bronze she won in the 69-kilogram competition.

All four athletes’ samples tested positive for the synthetic anabolic steroid stanozolol. Chinshanlo also tested positive for the steroid oxandrolone, and Shkermankova tested positive for the steroid turinabol.

The IOC did not make clear on Thursday whether the medals would be re-awarded to other competitors. Taiwan’s Hsu Shu-Ching, who won gold in the 53-kilogram weight division in Rio this summer, would be next in line for the gold, while Russia’s Svetlana Tsarukaeva and Natalia Zabolotnaya could pick up golds in the 63-kilogram and 75-kilogram categories, respectively, as long as re-testing does not show inconsistencies in their samples.

The IOC stores samples for 10 years, which it retests when new screening technologies become available.

Chinshanlo, Maneza, Podobedova and Shkermankova will now likely be banned for a year by the International Weightlifting Federation, according to the Associated Press. The IWF has yet to comment on the matter.

Additionally on Thursday, the IOC ruled it would not strip the silver medal won by late Russian wrestler Besik Kudukhov in the men’s 60-kilogram freestyle event in London.  The IOC said it did not know Kudukov had died in a car accident in December 2013 when it first ordered the athlete’s samples be retested, and because the “process normally following” an adverse test result cannot be seen to conclusion in this case, the IOC on Thursday announced it would drop the matter and allow the original results to stand.

“The situation is unsatisfactory as it implies that Olympic results which would probably have had to be reviewed will remain uncorrected,” the IOC statement added.