Supermarket giant Tesco is considering whether to sue the firm that was constructing a rail tunnel beneath the site of its Gerrards Cross store after it collapsed last week.

The tunnel was being built by Jackson Civil Engineering prior to the construction of a supermarket on top of it. The section of track below the Buckinghamshire development is expected to remain closed for another two weeks.

Tesco may lodge a claim against the contractor to cover potential claims from the train operators, which sources suggest could run to £20m.

A spokesperson for the supermarket said: “We are discussing claims issues with other stakeholders and our advisers but await the outcome of investigations by the authorities before making a decision.”

Richard Neil, chief executive of Jackson, said the company was in talks with Tesco to establish responsibility for the collapse.

The HSE is investigating the cause of last Thursday’s collapse, in which 50 m of the 320 m tunnel fell away, leaving the track buried in the rubble and ash used to fill the surrounding cutting. Two sections of the tunnel remain unstable and may need to be pulled down.

Henry Bardsley, an engineer with Paris-based RFR said the tunnel may have collapsed because of a combination of unsuitable arch geometry and the possibility that the fill around the arch was inadequately compacted, which would cause the sides of the tunnel to be pushed out by the weight of the fill above. Bardsley said if this were the case the tunnel would need to be rebuilt.