The group were performing a rescheduled date at Liverpool’s M&S Arena when concert goers say the venue was emptied out just before 9pm.
A user on social media who was in the audience posted: “S club concert at M&S Arena… fire alarms went off and all evacuated.”
The M&S Bank Arena later confirmed the news, posting: “Tonight, as S Club were close to finishing their set at the arena, there was a minor incident which triggered a partial evacuation.
“The issue was resolved quickly and we were able to restart the show. We will be launching a full investigation.”
It comes after the group were forced to cancel the initial Liverpool date which was to be the second performance of their reunion tour.
A statement from Jo O’Meara, Rachel Stevens, Tina Barrett, Bradley McIntosh and Jon Lee read: “We’re beyond devastated to announce that tonight’s how in Liverpool has had to be postponed by the venue, due to them having an unforeseen technical issue impacting their power supply and therefore your safety.
“We can’t begin to express how sorry we are. Especially as we know so many of you have travelled great distances to join us tonight.”
S Club 7 shot to fame in 1998 and were originally made up of Jo, Rachel, Tina, Jon, Bradley, Hannah Spearritt and Paul Cattermole.
After Paul died from natural causes earlier this year, it was confirmed that his ex-girlfriend and former band mate Hannah would not be taking part in the tour.