A cleaner was working at Peicai Secondary School yesterday when he looked up and saw what appeared to be smoke coming out of his 12th-storey flat, down the road at Block 220, Serangoon Avenue 4.

Mr Lim Jian An, 58, immediately phoned his wife, Madam Chen Yi Zhu, 55, who was out shopping at the nearby Nex shopping mall. The couple lived in the three-room flat with their two sons.

"Nobody was at home when the fire started," said Madam Chen, a housewife. So she had to call a friend, who lives in the next block, to look out her window.

Madam Chen said she dialled 995 immediately after receiving confirmation from her friend of the fire.

The Singapore Civil Defence Force (SCDF) was alerted to the fire at about 11.15am. Firefighters forced their way into the flat and extinguished the fire using a water jet. No one was hurt. The fire gutted the room of one of her sons, which is believed to be where it had originated, and damaged the rest of the flat.

The cause is under investigation, SCDF said.

"We have lived here for more than 30 years without incident," said Madam Chen, who added that the family will be staying with relatives for a while.