Ryder and Black Caps team-mate Doug Bracewell have confirmed to management they were out at a bar until the early hours of Thursday.
New Zealand Cricket is looking into the incident and will not comment further until its investigation is complete.
Otago Cricket Association chief Ross Dykes said he was awaiting the outcome of NZC's investigation before deciding whether Otago cricket would take any disciplinary action.
Whatever is happening off the park, it is certainly not having a negative impact on Ryder's form.
The hard-hitting left-hander cracked an undefeated century for Otago in its Plunket Shield match with Central Districts in Nelson yesterday.
It was his fourth hundred in just his seventh first-class match for the province, having transferred south from Wellington at the beginning of the summer.
An Otago Daily Times request to interview Ryder yesterday was declined. The 29-year-old has been placed off-limits to the media but on Saturday he told Fairfax ''most of it's bollocks''.
Two other reports of Ryder drinking alcohol while in camp with the Black Caps have emerged.
Ryder was drinking with Black Caps and Otago team-mate Jimmy Neesham after New Zealand's dramatic tie with India at Eden Park late last month.
He also had a evening out with comedian Ben Hurley in Hamilton after the Black Caps were beaten by 203 runs by the West Indies on January 8.
Otago team-mate Ian Butler, who has been sidelined since the opening game of the summer with a chronic back complaint, defended Ryder when contacted yesterday.
''The people who matter don't really listen to what they [the media] say,'' Butler said.
''I reckon he [Ryder] is pretty chilled about it. Things like what happened the other night just get blown out of proportion. He is used to that and it certainly isn't affecting his cricket. I've just looked at the scorecard and he is on 100.
''From what I've seen in the gym with him, he has never shirked a session. He does the extra work. Look how much weight he has lost - it's incredible.''
Butler conceded it was ''probably not ideal timing'' to go out for a drink on the eve of a test match.
''But, again, we don't know the exact scenario, and I'm certainly not going to judge if I don't know the full story.''
Mr Dykes said until NZC's investigation was complete, ''I think it is inappropriate for us to say anything, really''.
''When they have dealt with it, we'll see what we need to do,'' Mr Dykes said.
Mr Dykes was unaware of any incidents while Ryder had been with the Otago squad, and said it was disappointing the incident had detracted from Ryder's wonderful summer for Otago.
''As a run-scorer, he has been fantastic.''
