Double lightning strike hits Arriva and FGW services
Thousands of rail passengers across south Wales are facing further delays after a double lightning strike on signals.
Network Rail said engineers had been working round the clock to repair the damage between Cardiff and Bridgend.
Arriva Trains Wales says trains are diverted via the Vale of Glamorgan line through Barry but it is having a knock-on effect on its Valley Lines service.
Cardiff to Swansea mainline services face 45-minute delays.
Arriva Trains Wales (ATW) said it did not know when the line would re-open.
It had been hoped damage to signal equipment in the Llantrisant area at about midnight on Wednesday would have been repaired by 04:00 GMT on Thursday.
ATW said Network Rail and BT engineers had been working through the night, but the problem had not been fixed.
The line between Cardiff and Bridgend has been closed, and an emergency train plan introduced.
All normal Bridgend to Cardiff services via the Vale of Glamorgan are cancelled and replaced by the Manchester to Carmarthen/Milford services, which are diverted via the Vale of Glamorgan line, calling at Rhoose, Llantwit Major and Barry.
ATW reported severe delays on five of the company's Valley Lines services during Wednesday evening's rush hour.
These were in addition to the extended journey times and replacement bus services provided for passengers between Cardiff and Bridgend, calling at Pontyclun, Pencoed and Llanharan.
The Cardiff to Maesteg service is only operating between Bridgend and Maesteg, where a shuttle train service is operating.
Delays have affected passengers travelling on First Great Western (FGW) services as far west as Pembrokeshire as well as those travelling through Cardiff Central on Arriva services.
FGW passengers faced delays of up to 45 minutes between Swansea and Cardiff Central on Thursday morning.
Peter Leppard, ATW's operations director, said the lightning strike caused an "extraordinary amount of damage" and specialist help had been drafted in.
He told BBC Radio Wales he hoped - but could not guarantee - that repairs would be completed on Thursday, adding: "At the moment people are a bit stumped".
Mr Leppard apologised to customers, who he said were having a tough time, adding: "Please allow quite a lot of extra time for your journey.
"We will get you there, but please don't expect to get there terribly quickly."
Network Rail - which owns and operates the railways - said temporary signals were in place to allow some trains through Cardiff and Bridgend.
It added: "Network Rail engineers have been working round the clock since the incident and aim to restore services as soon as possible.
"There are delays and limited services on Cardiff and Bridgend and passengers are advised to check their journey time with their train operators or the National Rail inquiries before they travel."