Former health minister Keheliya Rambukwella is to be questioned over the importation of substandard human immunoglobulin vaccines.
That is on the basis of a claim by ex-health secretary Janaka Sri Chandragupta to the CID that he had acted on the orders of his minister.
Once quizzed, it will be decided if Rambukwella is to be named a suspect or a witness in the case relating to the scam, said CID sources.
Presently in remand custody, Chandragupta is likely to be named the chief state witness.
Additional secretary to the ministry Saman Ratnayake is to be interrogated as well.
The CID is presently going through the files of a number of top health ministry officials.
Although the requirement had been 7,500 vials of the vaccine, as many as 22,500 vials of a substandard quality had been imported, with Rs. 1,000 million allotted for the purpose.