The officer said the investigations are now focused on agency commissions being paid out by New Zealand education providers that had enrolled the students on fraudulently obtained visas, in the hope of identifying the agents on the receiving end.
Risk-profiling rules were relaxed in July last year for Beijing, and officers were told to stop verifying most academic qualifications gained in China by visa applicants.
He had earlier said New Zealand became "a magnet for agents wanting to put through fraudulent students" after this, and a move to allow students to apply for visas online would further encourage fraud.
"The investigation into the fraud is continuing, but if there is any evidence of criminal offending in China we will refer this matter to the Chinese authorities," said Michael Carley, Immigration NZ's operations support manager.
Of the 229 students who are in New Zealand, a total of 49 have so far been found and served deportation liability notices. Among them, 12 have been deported and four left willingly, but 16 have written to the agency requesting their deportation notices be cancelled.
"Each case is being considered on its merits," Mr Carley said.
From next year, foreign students can apply online following a $75 million overhaul of the agency's computer system. The system is expected to speed up processing times, and provide greater use of biometric identity checks and centralise immigration decisions so that they are made within New Zealand.
The agency employs 44 Chinese staff at the Beijing branch who carry out the same duties as officers in New Zealand.