In an early morning tweet, Mr Kejriwal said, "Compliments del police 4 bursting espionage rkt. During interogations, police shud try to reach top people, who wud benefit from leaked info."

Among those arrested yesterday were Shailesh Saxena of Reliance Industries Limited (RIL), Rishi Anand of Anil Dhirubhai Ambani Group (ADAG), Vinay Kumar of Essar and KK Naik of Cairn India. All these are high-ranking officials in their respective companies.

NDTV has accessed the FIR or First Information Report in which the police outlines its charges against seven people arrested earlier for selling classified information to energy companies, oil firms and consultants.

The FIR says that the stolen documents included information that was to be used by Finance Minister Arun Jaitley in his Budget speech on February 28, said sources. The Budget is regarded as a top-secret document till it is shared by the Finance Minister in Parliament. News of the leak came three days before the Budget Session of Parliament begins.

"On the basis of preliminary investigations, we can say these documents had been obtained by independent energy consultants... and certain companies working in the field of energy," said Delhi Police chief BS Bassi.

He said he did not want to name the companies involved at this stage of the investigation, but Reliance Industries, one of India's biggest business conglomerates, said one of its officials had been detained in connection with the case. "We are determined to cooperate in every possible manner," a Reliance official said, requesting anonymity.

Oil Minister Dharmendra Pradhan told NDTV that the leaks had been taking place for years, and that it was intelligence agencies and the government who alerted the police, which then conducted a major sting operation to catch the suspects red-handed as they entered the Oil Ministry on Wednesday night.

The accused include former senior journalist Santanu Saikia, who ran an oil industry portal, and two government officers. Mr Saikia's press accreditation card, which allows access to most government establishments, was cancelled by the government on Friday.

The accused were taken to the Oil Ministry on Friday by the police in an attempt to recreate the crime.