Peter was flown to Delhi at around 8 PM after the agency secured extension of his custody from a Mumbai court till November 30.
Sources said CBI is looking into his alleged investments abroad and custodial investigation was necessary to further the probe. The sources also did not rule out the agency subjecting him to scientific tests like polygraph, brain-mapping etc.
Peter (59), husband of prime accused Indrani Mukerjea, was arrested on November 19 and later taken to New Delhi for two days for questioning by senior CBI officials and experts on the financial trail in the sensational murder case before being brought to Mumbai this morning.
The CBI has also sought Interpol's help in seeking access to overseas bank accounts of the Mukerjeas.
As per CBI, which had claimed financial transaction as the motive behind Sheena's murder, investments of crores of rupees were made by the Mukerjea couple and that "Indrani and Peter had formed various companies during 2006-07 and invested Rs 900 crore in them."