New Delhi
The Enforcement Directorate (ED) investigation is related to a case of acquisition of alleged illegal assets abroad.
Special CBI Judge Arvind Kumar extended the ED's custody of Thampi by four days.
ED advocate Amit Mahajan said the probe was incomplete and his further custody was required to confront him with two persons.
The probe agency, however, did not disclose the names of the persons who will be called to join the investigation.
Thampi was produced before the court after his three-day ED custody ended.
The case relates to allegations of money laundering in the purchase of a London-based property, which is allegedly owned by Congress chief Sonia Gandhi's son-in-law Robert Vadra.
The property is located at 12, Bryanston Square, and is worth 1.9 million pounds.
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