DERAILMENT OF a Central Line commuter train between Mile End and Bethnal Green last week has been blamed on unsecured materials falling onto the track, says the company maintaining the line, Metronet BCV.
According to Metronet, a 'bale' of material fell onto the track, becoming entangled in the vehicle's wheels and derailing it.
British Transport Police said, six carriages left the track.
Balfour Beatty holds a licence to keep material in the store.
'However, others would have had access to the site, ' said a Metronet spokesman, who said that the Rail Accident Investigation Branch was leading the crash inquiry.
Passages and tunnels are frequently used to store materials needed for nightly track upgrades but, according to Metronet, no work took place at that site the night before the derailment.
RMT Union chairman Bob Crow said that private contractors posed a risk to the overall safety of the underground. '[The RMT wants] Ken Livingstone to take these contracts back inhouse before we have a disaster on our hands, ' said Crow.
Metronet BCV, which is responsible for maintaining and upgrading the Bakerloo, Victoria and Central lines has requested an extraordinary review by the PPP arbiter, to determine whether the contractor or client - London Underground - pays for around £1bn in overspends.
Metronet is jointly owned by Atkins, Balfour Beatty, Bombardier, EDF Energy and Thames Water.