At the end of last year, 15 female judoka sent a letter to the Japanese Olympic Committee complaining they had been subjected to harassment and physical violence by Sonoda at a pre-Olympic training camp.
The IJF said in a statement Friday that all of those involved with Sonoda in the abuse scandal have been suspended with immediate effect and that the independent inquiry will be opened soon. The names of those suspended were not given.
Sonoda tried to justify his behaviour by saying he was under tremendous pressure to produce gold-medal winners in London, and later resigned.
The IJF said it is "very committed to the educational values carried out by our discipline" and that the inquiry will examine the nature of the facts, people involved and background facts. No time-scale has been given for the investigation.
"Jigoro Kano created judo as a means of physical, mental and moral education, adding that competition is not a goal but a means of evolution for humanity," the IJF added.
Japan's sports minister Hakubun Shimomura has described the situation as the most serious crisis in Japan's sports history, where judo is centerpiece.