The university set up a screening panel last month to carry out a preliminary investigation of allegations of image manipulation in at least six papers produced in the laboratory of Paul Morgan (referred to in his publications as B. P. Morgan).
The university has now confirmed, in a letter to those who reported the allegations, that the panel has found "sufficient substance" in the allegations for it to instigate a formal investigation.
The letter adds that specific authors on some of the papers have already admitted responsibility for "certain aspects of individual allegations". However, the panel recommends that the formal investigation examine the conduct of all of the authors of each paper under scrutiny.
Allegations that images had been manipulated in four of Professor Morgan's papers, published between 2006 and 2012, first appeared on the Science-fraud.org website in July.
Last year another paper from Professor Morgan's lab was retracted from The Journal of Immunology after a Cardiff inquiry concluded that its corresponding author, Rossen Donev, had been solely responsible for inappropriately manipulating images.
Dr Donev, now a lecturer at Swansea University, is also an author on most of the papers currently being examined.
Professor Morgan, who is also a member of the Medical Research Council's governing council, has published 172 papers since 1998, and 35 review articles or chapters in the same period, according to Cardiff.
One of the papers under investigation, "Modulation of CD59 expression by restrictive silencer factor-derived peptides in cancer immunotherapy for neuroblastoma", published in Cancer Research, is listed on the Cardiff School of Medicine's website as one of its key publications of 2008.
A Cardiff University spokeswoman said: "Following evaluation of the allegations the initial screening panel has recommended that a Formal Investigation Panel be convened to consider a number of allegations in accordance with section six of the University's Procedure for Dealing with Allegations of Misconduct in Academic Research.
"The university's procedure is in line with guidance issued by the UK Research Integrity Office, to which the university subscribes. We need to await the outcome of the Formal Investigation Panel before offering any further comment."