A blocked drain caused glass panels around a condominium's fifth-floor swimming pool to shatter, sending broken glass and water cascading onto a carpark below, an investigation has found.

The Building and Construction Authority (BCA) found that overflowing water from the outdoor infinity pool at the Cradels condo in Balestier was caught in the narrow drain between the pool wall and the glass wall, causing water pressure to build up and the glass panels to eventually give way.

No one was hurt during the July 8 incident.

A professional engineer appointed to investigate said the glass panels had been installed to protect people from falling.

"They are not intended or designed to hold any prolonged overflow of water from the swimming pool," the BCA told The Straits Times.

Cradels managing agent Creation Management has closed off the entire common area on the fifth floor, including the swimming pool, barbecue pits and the gym, on the BCA's instructions.

A Creation spokesman said the company is looking into the repair works that need to be carried out. Plans will have to be submitted to the BCA for approval prior to construction.

When The Straits Times visited Cradels on Monday, the pool was still empty and no construction work had started.

Residents have been moving into the high-rise development, which has 125 units, since February last year.

One resident, who wanted to be known only as Ms Chen, said in Mandarin: "I used the pool the last time ... I am concerned there were no safety measures in the design."

The BCA will now be issuing an advisory to remind building owners to carry out regular inspections and proper maintenance of any drainage systems located near such safety barriers, to ensure that incidents such as this do not happen again.