The Cambrian line between Aberystwyth and Shrewsbury has reopened today (Monday).
In a statement, Transport Secretary, Ken Skates, MS, confirmed the line has reopened and Transport for Wales has begun running services again.
Mr Skates added: "The investigation teams have concluded their site-based investigation, and engineers have removed the damaged trains from the site.
"The investigations will continue off site, and it remains important that we provide the Rail Accident Investigation Branch, Office of Road and Rail and the British Transport Police the time and space to do this.
"Over the weekend Network Rail have undertaken thorough checks and safety inspections.
"The incident may continue to cause some disruption in the coming days and weeks, including some temporary service amendments. Passengers are advised to check their journey before travelling.
"Over the last week I have been in close contact with Transport for Wales and other agencies to ensure that passengers and staff who have been affected by the incident get the support they need.
"Transport for Wales have established a dedicated helpline, staffed by experienced advisors to provide assistance to the 41 passengers who were on board the two trains. "This has included the offer of counselling services alongside welfare checks and other practical measures such as re-uniting passengers with luggage left on the trains following the incident. In addition, Transport for Wales have also taken steps to provide appropriate support for rail staff who have been affected by the incident.
"I am grateful to all of those working in the rail industry who worked tirelessly since the incident to support those affected, and to enable us to begin operating these important services once more.
"Furthermore, I am grateful to the local community and passengers for their patience during this time."
The nearby A470 at Talerddig was due to close this week for essential repair work, but this has now been postponed to the new year.