"If there is any fresh set of facts, we can always re-look the case," SN Pradhan said.
There were "procedural irregularities" in the initial investigation of the drugs-on-cruise case involving Bollywood star Shah Rukh Khan's son Aryan Khan, the chief of the Narcotics Control Bureau (NCB) admitted on Friday, adding that action will be taken against those responsible for the lapses.
"Some procedural irregularities were found in the initial investigation by the local (Mumbai) unit. SIT (Special Investigation Team) had to take over. And that happens in the rarest of rare cases," SN Pradhan, the Director-General of the NCB, told NDTV.
"In an investigation, subsequent facts always clear up the matter. I would not immediately jump to blaming the initial unit because they must have had their reasons," he added.
Mr Padhan said the agency decided to not name Aryan Khan as an accused in the chargesheet "when it was clear that there was no possession and no corroborative evidence".
"If there is any fresh set of facts, we can always re-look the case," he said.
On action being taken against former NCB officer Sameer Wankhede and the unit accused of the lapses, he said, "We have already launched an inquiry into the vigilance allegation. The SIT has come up with gap areas which were in the initial investigation. So, on the basis of that, appropriate action will be taken."
Mr Pradhan also agreed that the agency should not have relied on purported WhatsApp messages to call Aryan Khan "a regular user of drugs", someone who "indulged in illicit drug trafficking", and was involved in the "procuring and distribution of drugs".
"The principle of WhatsApp chat has already been pointed out by the honourable court that WhatsApp chats cannot stand without corroborative evidence. In itself, it does not mean much," he said.
Eight months after his sensational arrest and spending over three weeks in jail, Aryan Khan's name was cleared by the NCB, which said they had not been able to find "sufficient evidence" against him and five others.
Aryan Khan was among 20 people arrested in October from a cruise ship off Mumbai, and drugs had been found on some of those arrested.
In November, the NCB headquarters removed Sameer Wankhede from the probe and transferred the case and five more from Mumbai to a Delhi-based SIT formed under its Deputy Director General Sanjay Kumar Singh.
After missing its deadline to file a chargesheet, the agency received a 60-day extension from a special court.