Crews from South Kirkby, Pontefract and Cudworth were called to tackle the blaze on Highfield Road in Hemsworth just after 10pm.
A spokesman for South Kirkby Fire Station said the newsagents had been locked up for the night.
But a couple of hours later, the owner, who lives opposite, spotted smoke coming from the building and raise the alarm.
He said: "When we pulled up it was quite heavy with smoke."
The fire is believed to have started from an electricla issue with a firdge or freezer.