FIRE crews deployed a thermal imaging camera after fire broke out at the Wales National Pool, Swansea.
They were called to the sports complex, off Sketty Lane, at 6.24pm this evening and stayed for around one hour.
There are no reports of any injuries.
Mid and West Wales Fire and Rescue Service said the fire involved electrical gear at the building's "plant room".
Crews from Swansea West and Swansea Central, wearing breathing apparatus, tackled the blaze with extinguishers containing carbon dioxide.
It is unclear how many people were in the £11million complex at the time, or whether they had to leave.
An answer phone message at the pool said the facility was closed due to a technical problem, and that it may not reopen tomorrow morning.
Swimmers and gym users are advised to phone the pool, or log onto the Wales National Pool website, before travelling there.
According to the pool timetable, recreational and lane swimming was due to take place in the 25m and 50m pools at the time of this evening's fire.
The Wales National Pool opened in 2003 and has been the training base for Olympians including Swansea's Georgia Davies and Paralympian golden girl Ellie Simmonds.