An imposed rail speed limit brought in due to severe weather was broken by a train as it passed by Sanquhar, investigators said.
Blanket restrictions were introduced across most of the rail network in Scotland on February 21 as Storm Franklin brought strong winds and heavy rain.
A 50mph speed limit was put in place to combat the bad weather.
The Rail Accident Investigation Branch (RAIB) found that a ScotRail service from Glasgow to Carlisle, via Kilmarnock, was travelling at its usual maximum speed of 70mph after passing Sanquhar at 9.03am.
It's believed the driver had been correctly informed about a speed limit between Kilmarnock and Gretna until 9am, but was not told it had been extended until 12.30pm between Sanquhar and Thornhill.
This incident was part of a trio to take place on the same morning.
The RAIB said: “The incidents show examples of three different mechanisms which resulted in the intent of the BESR (blanket emergency speed restriction) not being met, and in trains potentially travelling too fast for the prevailing conditions."
After conducting a preliminary examination, it decided not to carry out a further investigation.
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