The Narcotics Control Bureau (NCB) has taken away the controversial cruise drugs case, in which Shah Rukh Khan's son Aryan Khan was arrested, and five others from the agency's Mumbai zonal unit headed by Sameer Wankhede and transferred their investigation to its operations unit based in Delhi, officials said on Friday.

Senior officer Sanjay Singh will now be in charge in the drugs-on-cruise case, including the five others.

The action has been taken on "administrative grounds", and as these six have "wider and inter-state ramifications", they have been transferred to the operations unit in Delhi, NCB Deputy Director General (north-west region) Mutha Ashok Jain told PTI.

He said the order for the transfer of cases has been issued by NCB Director General (DG) S N Pradhan.

Wankhede, who is facing a number of personal and service-related allegations, will continue to be the zonal director of the agency.

The NCB had arrested Aryan Khan and at least 19 others in the drugs on cruise case on the intervening night of October 2-3 and Wankhede is facing a departmental vigilance probe after an independent witness in the case alleged extortion bid by those involved.

A team from the Delhi NCB operations will camp in Mumbai to take the probe in these cases forward, officials said.

The agency's Deputy DG, South-Western Region, Mutha Ashok Jain told reporters in Mumbai that this is an administrative decision and a team of Delhi NCB is arriving in Mumbai on Saturday to probe the six cases.

Wankhede refuted that he has been "removed" from the investigation in the Aryan Khan case and said the agency's move is about coordination between NCB teams of Mumbai and Delhi.

However, Maharashtra Minister Nawab Malik, who had launched a tirade against Wankhede and levelled several allegations against him, said the NCB officer's removal from the case "is just the beginning".

''Sameer Wankhede removed from 5 cases including the Aryan Khan case. There are 26 cases in all that need to be probed. This is just the beginning... a lot more has to be done to clean this system and we will do it," the NCP leader said.