A spokesperson for the London Fire Brigade said that they were called at 9:09 a.m. and that they have crews investigating the incident.
According to a spokesperson from London Fire Brigade there are three fire engines at the scene.
The fire alert was activated by smoke coming from a faulty train, according to media reports.
The incident has led to delays and suspensions on the Underground network. Euston Station has since reopened and trains are now stopping as normal.
Euston station is Britain's sixth-busiest train station.