The Central Bureau of Investigation (CBI) may have filed chargesheets claiming Satyendra Dubey was killed because the accused wanted to rob him of Rs 4,000 but it’s now set to file its first corruption case based on Dubey’s letter to the Prime Minister.Criminal action will soon begin—top sources said, over the next few days—against at least two contractors who have been awarded Golden Quadrilateral projects on the NH-2 stretch along with several other sub-contractors.The CBI Director, U S Mishra, has given the go-ahead for action which could begin with a preliminary enquiry (PE) or an FIR. If the action is taken under the Prevention of Corruption Act, as is being contemplated, it would mean some officials of the National Highway Authority of India (NHAI) may face criminal action as well.This comes at a time when the Supreme Court is hearing the very same allegations following a PIL filed on the subject. As reported earlier, the petitioners have now given the apex court an affidavit containing a list of specific allegations.Dubey, an IIT Kanpur graduate and an engineer with the NHAI, had highlighted instances of corruption in the Golden Quadrilateral project in his letter to the Prime Minister. The letter was leaked and Dubey was shot dead in Gaya in November last year.The CBI has now zeroed in on the blatant manner in which the GQ projects were sub-contracted (often several times over) in violation of guidelines and the poor quality of work on the stretch in Bihar and Jharkhand.The CBI estimates that the loss due to sub-contracting and shoddy implementation would be to the tune of Rs 10 crore.Some of the sub-contracted works that the CBI has taken note of include the the drainage layer for about 100 km and embankments of around 40 km. The CBI found that the sub-contracting for these works violated all norms and specifications.In his letter to the NHAI and the PMO, Dubey had listed irregularities under five different categories but on scrutiny, the agency found specific details and corraborative documents only in a few.After filing the first case, the CBI will ask the NHAI to submit the missing documents to gather evidence in other cases.