Aniel Mathrani, India's former ambassador to Croatia, whose reported claims in connection with the Volcker issue have triggered a political storm, was on Sunday questioned by a team of officials from the Enforcement Directorate and Intelligence agencies.

Mathrani, who arrived in New Delhi late Saturday night from Vienna, was interrogated by officials from the Intelligence Bureau and the Research and Analysis Wing at an undisclosed location, sources said.

The former envoy was questioned about the statements he had made about former External Affairs minister K Natwar Singh and a Congress delegation visiting Iraq in 2001, where he had claimed that the party was allocated 'oil coupons' as a part of the United Nations Oil-for-Food programme.

• Natwar knocks at 7, Race Course Road

He was also questioned about Singh's role in the entire issue as also the alleged involvement of Jagat Singh and Andaleeb Sehgal, they said.

Mathrani's claims to a news magazine that Singh was involved in getting 'oil coupons' for his son Jagat and friend Andaleeb triggered off a political storm, with the issue rocking both Houses of Parliament and the opposition demanding the resignation of Congress president Sonia Gandhi [Images] as the chairperson of the National Advisory Council.

Following opposition's demands, Prime Minister Manmohan Singh [Images], in a statement in the Lok Sabha, said his government was 'determined to go to the root of the matter and establish the truth or otherwise of these references'.

• Mathrani does a volte-face

The government had also said that Mathrani had been 'transferred back' and the process had begun to send his replacement.

Complete coverage: The Volcker Report - The Indian angle