The CBI on Monday started questioning Delhi Deputy Chief Minister Manish Sisodia in connection with the alleged scam in Delhi excise policy being probed by it, officials said.

Sisodia arrived at the agency headquarters around 11.15 am and was taken straight to the first floor of the Anti Corruption Branch, they said.

After completing the necessary formalities, he was subjected to questioning about Delhi government's excise policy, his relations with other accused named in the FIR and documents recovered during searches in the case, the officials said.

The CBI is also questioning Raghava Reddy, the son of YSRCP Lok Sabha MP Magunta Sreenivasulu Reddy, in the case, they said.

Before arriving at the central probe agency headquarters, Sisodia went to his party office in the morning from where he proceeded to Rajghat. A large number of his supporters gathered outside his residence and joined him on the way to the CBI office.

Delhi Police has made tight security arrangements and prohibitory orders have been in place around Sisodia's residence on Mathura Road, officials said.

The CBI had registered an FIR in a special court here in August against Sisodia and 14 others under various sections of the Indian Penal Code (IPC), including 120B (criminal conspiracy) and 477A (falsification of records), and section 7 of the Prevention of Corruption Act, which deals with taking undue advantage to influence a public servant by corrupt or illegal means, or by the exercise of personal influence.

Delhi Lieutenant Governor Vinai Kumar Saxena had recommended a CBI probe into alleged irregularities in the formulation and execution of the Delhi excise policy, which was brought out in November last year, the officials said.

Following the registration of the FIR, the CBI had conducted searches at the premises of Sisodia and opened his locker at a bank in Ghaziabad, they said.

The FIR has flagged payments in crores allegedly made to "close associates" of Sisodia by Sameer Mahendru -- the owner of Indospirits -- one of the liquor traders actively involved in irregularities in the framing and implementation of the excise policy.

The FIR alleged that Sisodia's "close associates" Amit Arora, the director of Buddy Retail Pvt. Limited in Gurugram, Dinesh Arora and Arjun Pandey were "actively involved in managing and diverting the undue pecuniary advantage collected from liquor licensees" for the accused public servants.