BALFOUR Beatty and Clough Smith are to be grilled by Railtrack after a series of incidents in which high-voltage cables were mistakenly cut outside Euston Station in London.
All cable recovery work was halted after the latest incident last week when a 650 volt cable was cut, disrupting services.
Railtrack is believed to have suspended the operatives involved.
It is understood that there have been at least three other similar incidents on the same section of track in recent months.
The work is being carried out as part of the £5.8 billion upgrade of the West Coast Main Line and involves replacing the cables.
Tilbury Douglas subsidiary Clough Smith is working for the Balfour Beatty-led Euston Alliance, which is re-modelling the station and approach tracks.
Health and Safety Executive records show that in the past two years there have been 12 reportable incidents involving contractors working at Euston, 10 of them involving injuries to contractor staff.
Operator Virgin Trains has threatened Railtrack with financial penalties unless disruption caused by the cable recovery programme is reduced.
Robin Gisby, Railtrack's director of network development, said: 'We have decided to convene a conference with all relevant parties to apply the lessons learned over the past few months and to agree how best to manage further development to the programme while minimising the disruption to existing services.'
Clough Smith operations director Ian Cramb said that the company was not in a position to comment before the result of an internal inquiry was known.
Construction News has learned that the Health and Safety Executive wrote to Railtrack last week highlighting its concerns about the work.
It has also emerged that Railtrack is investigating a further incident involving a contractor working at Proof House junction near Birmingham where a high-voltage cable was severed after the contractor had been on site for just three hours.