toxic fume warning light

[st_jimi]

i just bought a '01 plate 1.2 16v clio i drove it all the way down from leeds to cambridge all was fine apart from i made a quick pit stop at the service station 30mins from home when i set back on the travels the toxic warning light came on, i cant say there is any difference in power or running feel.

any ideas what it can be, ive seen in google some people say a cat problem others something wrong with the ignition coils and on here nothing to worry about it will go away

any help appreciated