Williams, 35, was expected to appear in court at a later date after admitting a charge of purchasing three vials of cocaine containing 2.4 grams (0.08 oz), the source said.
O'Connor, 26, will pay a fine for cocaine possession, the source added.
On Saturday, a judicial source said both players were drunk at the time of their arrest and were attempting to buy drugs worth about 200 euros ($211.10) and that the two sellers were also arrested.
Williams plays for French club Racing 92, while O'Connor is with Toulon. Racing 92 said in a statement on Friday that they had suspended Williams over the incident.
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($1 = 0.9474 euros)
(Reporting by Chine Labbe; Writing by Bate Felix; Editing by Ken Ferris)
