The Criminal Investigations Department arrested former DIG Prasanna Nanayakkara this morning in connection with the Lasantha Wickrematunga murder. 

Nanayakkara was arrested over charges of concealing evidence with regard to the former Sunday Leader Editor's murder, Police sources said. 

Nanayakkara was under investigation for the mysterious disappearance of Wickrematunga's note book which was found inside his car,  by the Police, following the murder. 

It was revealed that Wickrematunga had written down the numbers of the motorcycles following him, in the notebook, a few minutes before his killing. 

The notebook went 'missing', mysteriously, while in Police custody. 

The CID suspects that the disappearance of the notebook was part of the 'cover-up plan' of the murder allegedly committed by a group affiliated with the former government's defence apparatus. 

Former IGP Jayantha Wickremaratne and DIG Nanayakkara had been questioned by the CID before, over the same incident.