New Delhi, May 20 -- The Central Bureau of investigation (CBI) on Tuesday arrested a Colonel posted with the Army Ordnance Corps, Eastern Command, in a Rs.50-lakh bribery case, agency officials said. The Colonel, posted at Fort William, Kolkata, was taken into custody in Kolkata under prevention of corruption act and is being brought to Delhi for further interrogation, officials said, adding that other "unknown officials" are also under the scanner. The first information report (FIR) registered by CBI on May 18, said the Colonel was accused of indulging in corrupt practices for favouring a Kanpur-based private person and his firm in the award of tenders, approval of substandard samples and clearing of pending and inflated bills in lieu of b...