In a blow to Arvind Kejriwal, CBI today arrested his (Delhi CM's) Principal secretary Rajendra Kumar and four others in a corruption case. CBI officials had last year carried out searches at Delhi Secretariat while investigating corruption charges against Rajendra Kumar. Rajendra Kumar has emerged as the kingpin of the 50 crore scam which first started activity in 2006, CBI sources have said. There are allegations related to bribery and abuse of position against them, further probe is underway, said CBI Spokesperson, RK Gaur. All 5 accused including Rajendra Kumar will be produced in Delhi's Patiala House court tomorrow.\u00a0Deputy Secretary in Kejriwal's office, Tarun Sharma is among the 5 arrested by the CBI. Aam Aadmi Party (AAP) reacted strongly to the news, accusing the Modi government of attempting to paralyse the functioning of Delhi government and trying to "finish off" Arvind Kejriwal. Kumar, an IIT alumnus, is accused of favouring certain companies in awarding government contracts from 2007-2014. The raids had been carried out in December 2015, and Kejriwal had then challenged the PM Narendra Modi to dig out anything against his government. He had also alleged that the target of CBI raid was he himself and not senior IAS official Rajender Kumar, whose office and residence were searched. \u201cWhen Modi cudn\u2019t handle me politically, he resorts to this cowardice. Modi is a coward and psychopath,\u201d Kejriwal had tweeted, in an attack on Modi. The AAP had also launched a no-holds-barred attack on the Centre with its spokespersons calling it a \u201cblack day\u201d in Independent India\u2019s history. \u201cThe Modi government has imposed an undeclared emergency in Delhi. Never ever a Chief Minister\u2019s office has been raided. It is a black day for India\u2019s democracy,\u201d AAP Spokesperson Raghav Chadha had said. The 1989 batch IAS officer, who held several important positions under the previous Congress government, was appointed Principal Secretary to the Chief Minister in February when the AAP wrested power for the second term. Kumar is known to be close to Arvind Kejriwal.