Chorley's main swimming pool has been forced to shut after its water levels "unexpectedly dropped" overnight.
All Seasons Leisure Centre in Water Street said it will not be opening its main pool today (June 27) due to "unforeseen circumstances".
Active Nation, which operates the leisure centre, said an investigation is underway after the pool was discovered drained this morning.
A spokesman for Active Nation said: "An investigation is underway and the pool will remain closed until the problem is fixed.
"We are working hard to resolve the issue and will keep you updated.
"We apologise for any inconvenience this may cause."
Chorley Marlins amateur swimming club said it had been forced to cancel its training sessions today due to the mishap.
It is understood that the pool was inadvertently drained after the leisure centre closed last night (June 26).
A spokesman for Chorley Council said: "The pool at All Seasons Leisure Centre is closed this morning as water levels dropped unexpectedly overnight and the problem is being investigated."