Transport Minister Ken Skates told the Senedd thatsafety was the Welsh government’s “prime concern”.

Plaid Cymru’s Senedd member for Dwyfor Meirionnydd, Mabon ap Gwynfor, said he had received messages from constituents worried a crash could happen again.

Skates promised lessons would be learned “as soon as possible”.

Network Rail and Transtport for Wales (TfW) said in a joint statement it was a “low-speed collision”.

TfW chief operating officer Jan Chaudhry van der Velde said he could not discuss the causes of the accident but said its rail accident investigation branch arrived at the scene on Monday night and remained there.

A full report would take several months to be processed, he said.

“The line is largely made up of stretches of single line where trains use one line to travel in two directions and where trains need to pass each other, we have passing loops,” he said.

“Where the collision happened there is one of these passing loops,” he added.

Local councillor Elwyn Vaughan said the crash was “a shock and a surprise”.

“It is a single track line, so that’s unusual in many contexts, but there are dedicated passing places,” he said.

“The norm would be one train parks there, and the other passes. The fundamental question is, why that didn’t happen last night?”

He said a new digital system to stop trains might be to blame, or leaves on the line, given the steep incline at the location of the crash.

The Rail Accident Investigation Branch (RAIB) deployed a team of inspectors to the site of the crash and once inspected, decisions will be made on the need for further resources.