Lalta Prasad and Rakesh Kumar were taken to Shastri Bhawan on Sunday by the Crime Branch.

Sources, meanwhile, said that police had also stumbled upon another module operated separately from the those arrested so far and their "area of operation" was another plum ministry.

They added that a junior-level officer and some more corporate executives are under scanner in this connection and arrests are expected by Monday.

Interrogation of the five corporate executives also continued at Crime Branch office at Chanakyapuri here. The Crime Branch is trying to understand how the stolen documents were utilised for gains for their respective companies and whether top executives were also involved in the entire episode.

Sources said that two top officials of a major oil firm were summoned to join investigation but while one is down with swine flu, the other is out of country. Police may soon summon some senior officials for questioning as well.

"We have questioned the people who are in our custody and a team, which included policemen and experts from the ministry, is examining the documents recovered so far.

"We took Lalta Prasad and Rakesh Kumar to Shastri Bhavan today to further understand their modus operandi and gather evidence. We chose to do it today as being a Sunday, not many people were present and our work became easier," said a senior police official.

We also recorded the statement of the key maker who had made the duplicate keys of the ministry locks and he is our "main witness" in the case, he added.

Producing the five corporate executives arrested on Friday before Chief Metropolitan Magistrate Sanjay Khanagwal, the police said, "National interest was taken for a ride in the case.

"Documents related to national security have also been recovered. This may attract charges under the Official Secrets Act," police had said.

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