The Welsh Long Course Swimming Championships' final two days had to be postponed amid fears that a "popped" light had sent debris into the Wales National Pool in Swansea.
A spokesman said the 50m pool was closed "immediately as a precaution".
Swim Wales chief Robert James said: "Three lights blew out... the bulbs burst, depositing glass into the pool and poolside areas."
The two remaining days of competition could be held on 18-19 April.
James added: "This incident is viewed as very serious and therefore after discussing with the pool management we could only cancel today and tomorrow's events.
"This has left the competition halfway completed and we are looking for alternate dates."
The pool spokesman added: "Swim Wales agreed with the decision and the championships have now been moved to later in the month.
"The pool is being checked for debris and it will be reopened as soon as possible. In the meantime we apologise for the inconvenience caused."