At shortly after midnight on February 5, a man set a number of newspapers alight and placed them on a seat before walking away, British Transport Police (BTP) said.
The blaze happened on board a Metropolitan line Tube train between Northwick Park and Wembley Park stations.
Staff at Wembley Park discovered and extinguished the fire, which caused around £4,000 worth of damage, police said.
Officers from BTP have now released CCTV images of a man they believe may have information which could help investigate the arson offence.
A spokesman for the force said: “Officers believe the man shown in the images may have information which could help the investigation.”
Anyone with information should contact BTP on 0800 40 50 40 or text 61016 citing reference 158 of 28/02/18.
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