Urging caution yesterday, Home Affairs Minister K. Shanmugam said there is no evidence at this point to suspect the reliability of the certification process for cladding materials used on buildings.
Mr Shanmugam noted that the certification system relies on laboratory reports of international and local institutes with sound reputations worldwide.
He gave this response in Parliament to Workers' Party Non-Constituency MP Daniel Goh, who had asked how non-compliant combustible panels were given certificates that allow their use on external facades in Singapore.
The cladding issue drew wide attention after an inferno last June that killed 71 people in a London residential high-rise was traced to combustible cladding used on the building.
Last month, the Singapore Civil Defence Force (SCDF) carried out tests on buildings as part of a wide investigation into the use of aluminium composite cladding.
It found that two brands of aluminium composite panels used as cladding material - Bolliya and Bolli-Core FR - did not meet the required Class "O" standard, the most stringent standard for fire-rated combustible panels.
But the panels had been given Certificates of Compliance that rate them as Class "0".
Seven buildings have since been found to use these two brands.
Three have removed the panels, while the remaining four are in the process of taking them down, said Mr Shanmugam, who is also the Law Minister.
The same investigation last year uncovered 35 buildings using a brand that also failed SCDF's fire safety checks.
Panels made by the brand, Alubond, contributed to a fire at an industrial complex in Toh Guan Road, killing one person.
The panels have been removed from 17 buildings, while owners of the remaining 18 have yet to complete taking down the panels.
The investigation into the use of cladding in Singapore is ongoing, said Mr Shanmugam.
He added: "We will be investigating all possibilities, including whether there could be manufacturing defects, and differences between samples and actual material."
Dr Goh asked if other brands of cladding will be tested.
Mr Shanmugam replied that the SCDF has contacted industry partners, required qualified people to submit information about their buildings, and conducted a second round of checks, which was how the two cladding brands Bolliya and Bolli-Core FR were uncovered.
He said the annual audit by certification bodies in Singapore will be hastened, and this should cover all the other brands.