Tube maintenance firm Tube Lines could face large claims following the derailment at Camden Town last Sunday. The derailment left seven people injured, one seriously.
London Underground, a division of Transport for London, which has some of its insurance with St Paul, said its initial investigations suggested a problem with the track was the cause of the accident.
The tracks are maintained by Tube Lines.
Investigations are ongoing and London Underground confirmed that loss adjusters had been appointed.