Official sources said Vadra was required to rejoin the probe on Thursday as he needed to answer more questions on allegedly acquiring immovable assets in the United Kingdom.

They said the questioning of Vadra is underway and it is understood that he is being "confronted with" documents that the agency has obtained or seized as part of its probe in the case, including those linked to absconding defence dealer Sanjay Bhandari.

Vadra has also shared documents with the investigating officer of the case and has assured some more will be provided as and when he gets them, the sources said.

He was grilled for five-and-a half hours for the first time in the case on Wednesday. His lawyer said Wednesday night that Vadra had replied to every question put to him.

On Thursday, Vadra arrived at the ED office in Jamnagar House in central Delhi in an SUV at about 11.25 am, about an hour after his team of lawyers reached there.

After two hours of questioning, he left for lunch and returned about an hour later to resume the session.

The ED case against Vadra relates to allegations of money laundering in the purchase of a London-based property located at 12, Bryanston Square worth 1.9 million GBP (British pounds), which is allegedly owned by him.

The agency has told a Delhi court that it has received information about various new properties in London which belong to Vadra. These include two houses, one worth 5 million GBP and the other valued at 4 million GBP, six other flats and more properties.

Vadra has denied the allegations of possessing illegal foreign assets and termed them a political witch hunt against him. He said he was being "hounded and harassed" to subserve political ends.

Vadra's lawyer K T S Tulsi told reporters outside the ED office Thursday his client has not committed any wrongdoing.

A team of three ED officials, including the investigating officer of the case, has put across about two dozen questions to Vadra over two days.

His statement is being recorded under Section 50 (powers of authorities regarding summons, production of documents and to give evidence) of the Prevention of Money Laundering Act, as was done on Wednesday, the sources added.

His appearance before the ED acquired political overtones after his wife Priyanka Gandhi, appointed Congress general secretary in-charge of eastern Uttar Pradesh, accompanies him to the investigating agency's office on Wednesday. She took charge of her new post at the Congress national headquarters on Akbar Road shortly after that.

"He is my husband, he is my family...I support my family," Priyanka Gandhi said in a show of support to Vadra, who had returned from London earlier on Wednesday.

That was the first time Vadra had appeared before any probe agency in connection with alleged dubious financial dealings.

On February 2, he was directed by a Delhi court to appear before the central probe agency and cooperate in the probe after he knocked on its door seeking anticipatory bail in the money laundering case.

In December last year, the ED conducted raids in the case and grilled his close aide Manoj Arora, an employee of Skylight Hospitality LLP, a firm linked to Vadra, as well as others.

The agency told the court that it filed a PMLA case against Arora after his role cropped up during the probe of another case by the Income Tax Department under the 2015 anti-black money legislation against Bhandari.

It alleged that the London-based property was bought by Bhandari for 1.9 million GBP and sold in 2010 for the same amount despite incurring additional expenses of approximately 65,900 GBP on its renovation.

Seizing on the questioning of Vadra, the BJP has attacked the Congress and alleged he got kickbacks from a petroleum and a defence deal during the UPA rule.

Vadra is also expected to present himself before ED on February 12 in Jaipur in an unrelated money-laundering case related to a land scam in Bikaner. The Rajasthan High Court has directed him to cooperate with the agency in the case.