After a 19-month investigation, the National University of Singapore (NUS) today says that it has determined that one of its former scientists, the immunologist Alirio Melendez, has committed “serious scientific misconduct”. The university found fabrication, falsification or plagiarism associated with 21 papers, and no evidence indicating that other co-authors were involved in the misconduct, it says.

But the university would not identify the papers (although five of Melendez’s papers have already been retracted), nor release the report of the committee that investigated them. That tight-lipped approach mirrors two other investigations into Melendez’s work by the University of Liverpool and the University of Glasgow, UK, which respectively abandoned and concluded inquiries last year without publicly commenting on their findings.

“It’s standard procedure that for research-misconduct investigations such a report and the list of papers would be kept confidential,” an NUS spokesperson explained to Nature. She said that the university is now contacting journal editors and co-authors about each of the papers involved, and added that normally the university would not make a public statement at all, but in this case “the scientific misconduct uncovered was unprecedented”. When asked whether the report would remain permanently under wraps, she added: “I don’t think it will be released at a later date.”

The university did not reveal Melendez’s response to the charges; last year he told Nature that he was conducting his own investigations into other papers, which he agreed contained “questionable data”, but which he asserted were not his fault. Nature made efforts to contact him for this article without success.

The NUS launched its investigation in March 2011 after an anonymous letter alleged research misconduct in two papers. An inquiry committee looking into this subsequently extended its remit to cover around 70 papers, focusing on NUS-affiliated work, and the investigation was reported in Singapore’s Straits Times in October. Melendez — who left Singapore to come to the United Kingdom in 2007 — had subsequently worked at the Glasgow and Liverpool universities, which conducted their own investigations alongside NUS.

A cascade of retractions and alterations racked up while the NUS was investigating; it now totals five retracted papers, a correction and an expression of concern (the history can be followed on Retraction Watch). In autumn of 2012, it emerged that Melendez had resigned from Liverpool in November 2011, not long after the University of Glasgow concluded its investigation in October 2011. But Glasgow told Nature it would not comment on individual cases (as the Times Higher Education also reported).

Today, the NUS says that its committee “uncovered evidence of fabrication, falsification, or plagiarism associated with 21 papers, including the two in the original allegation. Based on similarities in the pattern of misconduct and in some cases sole authorship of questionable papers, it concluded that Dr Melendez has committed serious scientific misconduct. The Committee found no evidence indicating that other co-authors were involved in the scientific misconduct. NUS has started the process of informing the relevant authors and journals about the problems in these papers to ensure that the public scientific record will be corrected.”