New Delhi, June 9 (IANS) Himachal Pradesh Chief Minister Virbhadra Singh on Thursday reportedly "failed to explain the evidences" against him during questioning by the CBI here and he was summoned again on Friday for a second round of questioning in a case of alleged disproportionate wealth.

The 81-year-old senior Congress leader was questioned at the Central Bureau of Investigation (CBI) headquarters for around five hours and confronted with various "evidences" over Rs 6.03 crore worth of unaccounted assets.

"Virbhadra Singh was questioned over his different properties and assets. He had no explanations when confronted with the evidence against him," an official told IANS.

The official said the CBI has "fool-proof evidence" against Singh. He, however, declined to share the evidences of confiscated property by the agency against Singh.

"CBI has a fool-proof case against Singh, his associates and partners in criminal conspiracy regarding the assets acquired in the name of his children and wife," an official said.

The CBI has called the Chief Minister to appear before it for questioning on Friday.

The official claimed that Singh, during questioning, put the onus of explaining the assets of his wife and children on them. CBI sources said that his son, Vikramaditya, had claimed during CBI's preliminary enquiry that some of his assets were from the money provided by his father.

The probe against the Chief Minister and his family members was initiated following graft allegations against him during his tenure as the Union Steel Minister from 2009 to 2011.

The octogenarian Congress leader, who was questioned for the first time on Thursday, reached the national capital on Wednesday.

A case was registered on September 23 last year under the Prevention of Corruption Act against the Chief Minister, his wife Pratibha Singh, Life Insurance Corporation agent Anand Chauhan and associate Chunni Lal.

It was registered after a preliminary inquiry allegedly found that Virbhadra Singh accumulated assets worth Rs 6.03 crore in his name and in the name of his family members, which were disproportionate to his known sources of income.

"The FIR was the outcome of a preliminary inquiry which revealed that Virbhadra Singh, while serving (as union minister) during 2009-2012, had allegedly accumulated assets worth Rs 6.03 crore in his name and in the name of his family members which were found to be disproportionate to his known sources of income," a CBI official said last year.

"The other people named in the FIR had allegedly abetted the then union minister in committing the offence," he had said.

Singh moved the Himachal Pradesh High Court following CBI searches at his residences in Delhi and Shimla on September 26 last year.

The Himachal Pradesh High Court had on October 1, 2015 restrained the CBI from arresting or interrogating Singh or filing a chargesheet against him.

In November last year, the Supreme Court transferred the case to the Delhi High Court from the Himachal Pradesh High Court, saying the transfer was necessary "to protect the institution from embarrassment" and to "avoid further controversy".

However, the apex court did not pass any order to modify the Himachal Pradesh High Court order that restrained the CBI from arresting Singh.

The CBI urged the Delhi High Court to vacate the Himachal Pradesh High Court order, contending that the order was hampering investigation following which it on April 5 this year asked Singh why he did not join the investigation.