Potential bidders for the government's stake in public sector oil major Hindustan Petroleum Corporation will begin due diligence next week.

Reliance Industries will be the first firm to scrutinise the books of the company in which the government is selling its 34 per cent stake along with management control to a strategic partner, official sources said in New Delhi.

Each bidder has been given 12 days for the process, which will include access to the company's data room, inspection of HPCL's refineries at Mumbai and Visakhapatnam and select marketing terminals.

The other bidders for the country's second largest oil firm are British Petroleum, Kuwait Petroleum, Petronas of Malaysia, the Shell-Saudi Aramco combine and Essar Oil.

Lead manager HSBC has informed that the due diligence by bidders would be completed by mid-October after which price bids can be called for.

Though the inter-ministerial group had earlier this month fixed September 30 as the deadline before which the scrutiny should be over, HSBC has said the bidders' visit to the data room would be little delayed until October 4, the same time as the visit to HPCL's refineries would be completed. As for marketing terminals, the last date for all visits  by bidders would be mid-October, it said.

Sources said technical consultant Foster Wheeler has submitted the draft report to HPCL for comments before a final report is made while environmental consultant ENSR has sought more time to submit its draft report.