Damaged cables in Suffolk delay train services
Damage to signal cables in Suffolk has been blamed for disruption to train services into London from East Anglia.
The problems at Needham Market, near Stowmarket, reduced trains between Norwich and London to a two hourly service for part of the morning.
Services in Essex were also affected, National Express East Anglia said.
Network Rail said engineers were working on repairs and an attempt at cable theft could not be ruled out as the cause of the damage.
Services were not likely to be back to normal until the afternoon, the spokeswoman said.
"We are still investigating the cause of the damage and can't say for sure if it was cable theft or it wasn't," she said.
"We can't rule it out. We just don't know what caused the damage.
"Investigators are on site at the moment and their first priority is to fix the problem," she said.
Passengers on routes in and of London's Liverpool Street station faced cancellations and bus replacement services.
Cable thefts have hit train services several times over recent months.
A spokesman for the Association of Train Operating Companies said: "Cable theft causes thousands of incidents of disruption every year.
"Criminals' thoughtless actions lead to a significant number of delays and cancellations every week. The rail industry is working hard to tackle the organised gangs and opportunist thieves who are causing the problems.
"To deal with the problem more effectively, we need tighter regulation on the sale of scrap metal and tougher sentences for offenders."
The rail problems in East Anglia on Tuesday were further compounded by a broken-down freight train at Manningtree in Essex.
Operator National Express East Anglia said it was using buses between Stowmarket and Ipswich. An amended train service is also running between Cambridge, Ely and Stowmarket.