Network Rail has launched an investigation into the track maintenance record of contractor Jarvis after a series of accidents.
Seven people were killed in the Potters Bar crash
The owner of the railway network has called in Jarvis directors to question them about the company's working practices.
Network Rail bosses are furious following the latest accident involving Jarvis, when an express train was derailed outside London King's Cross last week.
The contractor admitted staff had failed to secure a signal at red.
Network Rail is conducting a top down inquiry into the company's management, supervision, working and training practices.
It is trying to find out if a one-off mistake or systems failure was to blame.
No-one was injured in the Kings Cross derailment - but it caused days of delays for commuters.
Jarvis had previously been carrying out overnight engineering work on the stretch of track where the train derailed.
The company confirmed the points should have been left so trains would continue straight ahead, but staff had "neglected" to reset them.
An investigation was launched by the Heath and Safety Executive.
The Kings Cross incident closely resembles the derailment at Potters Bar in November in which seven people died and 76 were injured.
Jarvis was the contractor at the centre of that case too and it is due in court next week over the incident.
In June, Network Rail announced Jarvis was the preferred bidder to replace defective track in the area around Potters Bar.
Families of victims and rail unions said they were astonished at the insensitivity of the decision.