The Reliance group's attempt to conduct due diligence at Hindustan Petroleum Corporation's refinery at Mahul near Mumbai was stymied by employees opposing the move.

Reliance executives were not allowed to enter the refinery premises and had to turn back though the HPCL management tried to intervene.

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About 1,000 members affiliated to several unions staged a dharna at the refinery on Friday.

They contended that due diligence should not begin till such time as the Supreme Court gave its verdict on a writ petition filed by the Oil Sector Officers' Association challenging the privatisation of the corporation without parliamentary approval.

The petition is slated to come up for hearing in the Supreme Court on September 1.

When contacted, a Reliance Industries' spokesman said, "No comment."

An HPCL executive confirmed there was a "slight problem" at the refinery near Mumbai, but he maintained "there was no problem as such and that the due diligence process was normal."

The due diligence process was kicked off on August 28 with HPCL's data room thrown open to prospective bidders.

Reliance executives visited the data room in Delhi and Chennai, besides visiting HPCL's depots at various locations.

Each bidder gets at least 12 days to scrutinise the books of the corporation before the process winds up in mid-October.

Several local as well as multinationals oil firms, including Shell-Aramco, BP and Petronas have evinced interest in the privatisation of HPCL. The government is divesting its 34.01 per cent holding and management control in HPCL.