The Central Bureau of Investigation (CBI) Tuesday began questioning former Karnataka minister and mining baron G. Janardhana Reddy and his brother-in-law Srinavasa Reddy in an illegal mining case, more than a week after arresting them.

After getting their custody for six days, the CBI shifted them from Chanchalguda Central Jail here to its office and began grilling them in connection with the alleged illegal mining in Andhra Pradesh's Anantapur district.

The CBI, which had registered a case against Obulapuram Mining Company (OMC) owned by Janardhana Reddy in 2009, will try to find out the involvement of government officials and others.

CBI Joint Director V.V. Lakshminarayana told reporters that they would question all those whose names might come up during the interrogation.

"We can question anybody and can conduct searches at any place," the official said.

"Let us see what comes out during the questioning (of the two accused)," he said after the special court sent them to CBI custody till September 19.

The investigating agency might seek custody of the two for more days.

"It depends on what information we get," he added.

Lakshminarayana said tests like narco analysis, polygraph and brain mapping may be done on the accused only after their consent, as directed by the Supreme Court recently.

Earlier, the special CBI court rejected the bail petitions of the two and sent them to the CBI custody.

The CBI court on Monday night reserved its orders after a marathon hearing on the bail pleas of the accused and on a CBI petition for the their custody.

Armed with the court warrant, a team of CBI officials led by Additional Superintendent of Police R.M. Khan later reached Chanchalguda Central Jail to take custody of Janardhana and Srinivasa Reddy, even as the lawyers of the duo moved the high court against the special court's order.

Additional Solicitor General (ASG) Vivek Kanka earleir Monday told the court that there is a lot the CBI wants to investigate by interrogating the two accused.

Terming the illegal mining as a huge crime syndicate spread over Andhra Pradesh and Karnataka, the ASG said it would not have taken place without connivance of the public servants from top to bottom.

"The CBI wants to find out the role played by public servants in granting permits for mining and transportation of iron ore and laying of roads in forest areas," he said.

"It is a huge activity and hundreds of people may be involved. We need to question the two, who are kingpins. It is a case of plunder of national wealth," Kanka said.

The CBI had also produced evidence like satellite images to the special court in support of its claim that there was no mining in 68.52 hectares area leased to OMC since 2007 and that iron ore mined illegally elsewhere was transported to the area.

The prosecution told the court that by questioning the duo it wants to find out the source of iron ore.

A battery of defence lawyers, headed by senior Supreme Court advocate Udai Lalit, sought the bail for the accused on the ground that the CBI case against them was politically motivated, mala fide and vindictive.

Lalit is the special public prosecutor in the 2G scam case being heard in a special court in Delhi.

The CBI arrested OMC director Janardhana and OMC managing director Srinivasa after raiding their houses on September 5 in Karnataka's Bellary district.

The same day, they were brought to Hyderabad and the CBI court remanded them in judicial custody till September 19.