Bollywood actor Arjun Rampal's troubles mounted as the Narcotics Control Bureau (NCB) grilled him for nearly 7 hours even as his Australian friend Paul Bartel was arrested in a drug related case investigation, official sources said here on Friday.

Bartel was reportedly in regular contact with Agisialos Demetriades, an alleged drug peddler, arrested by NCB in Oct., and the brother of Gabriella Demetriades, the live-in partner of Rampal.

An architect living in Bandra, Bartel was questioned by NCB on Thursday and early Friday placed under arrest in the same case in which Bollywood actress Rhea Chakraborty and at least 20 others have been arrested in the past three months of NCB probe.

Since around noon, Rampal was grilled by the NCB, after his girlfriend Gabriella was questioned for more than 12 hours spread over Wednesday-Thursday, while Bartel was quizzed on Thursday and arrested this morning.

Among other things, Rampal, 47, was interrogated on the nature of his links with Agisialos and Bartel, the seizures made during the raid conducted at his Bandra residence last Monday, and the role of Gabriella and others with drug peddlers.

Interacting briefly with mediapersons after he exited the NCB office, Rampal said: "I am fully co-operating with the NCB investigations. I have nothing to do with drugs. The medicine found at my residence (in the Monday's raids) was prescribed by a doctor. The prescription has been handed over to the NCB.... The NCB officials are doing a good job and I fully support them in their investigations."

Incidentally, Agisialos has been booked in another drug case after the probe revealed his connections with a Nigerian cocaine supplier, Omega Goodwin.

Both Bartel and Agisialos are known to Rampal as well as other filmdom personalities as the NCB tightens it grip on the Bollywood-drugs mafia cartels.

The NCB's Bollywood drugs angle probe was launched after the death of Bollywood actor Sushant Singh Rajput at his Bandra home five months ago - on June 14 - in which several prominent personalities like Deepika Padukone, Shraddha Kapoor, Sara Ali Khan, Rakul Preet Singh, Firoz Nadiadwala and others have been either questioned, arrested or raided, and many others said to be on the agency's radar.