A witness, Mark Ashbridge, took this picture of the small blast in Belfast city centre.
It appears people had been pushed back before the explosion occurred.
Mark says "the glow is the result" of the blast:
No injuries have been reported.
More top news
Carefully choreographed campaigns can become unstuck because voters have the power to peel back a politician's veneer.
Sherpas have been biologically wired over thousands of years to give them exceptional mountaineering skills, research shows.
Stanley May - who was a regular at the supermarket in Truro in Cornwall - hit his head on the wet floor.