Tampines resident Choo Keat Thin was watching television at 10am yesterday when he felt the floor shake and heard a loud "boom".
He found out that an exterior concrete sunshade above the window of his fourth-floor flat had partially dislodged and landed on the sunshade below.
The dislodged sunshade - about 5m long - was left balancing on the sunshade on the third floor. The other end of the dislodged sunshade was left hanging above Mr Choo's window.
"I was shocked to see such a big external structure fall off and my first thought was to call the police," said the 59-year-old car workshop owner. "There were many people walking below to go to the market and it could have killed someone."
A piece from the sunshade on the third floor chipped off, but no one was hurt in the incident at Block 201E, Tampines Street 23.
Mr Choo said: "I hope they do a thorough check as there are similar structures around."
Ms Ling He, a cashier at a food stall opposite the block, said: "I saw the whole structure fall and a smaller piece coming down. Immediately, many of our customers dispersed and left.
"If that one small chunk could damage the ledge, imagine what would have happened if the whole thing had come crashing down?"
When Ms Cheng Li Hui, an MP for Tampines GRC, was alerted to the incident at 10.25am, she told grassroots leaders to get the police to cordon off the area and contact the relevant agencies.
"For safety reasons, I told the shop owners to bring in their products from the corridor, and many of them decided to close their businesses since the area was being blocked off ," she said.
The dislodged sunshade was later safely removed by a crane, with a professional engineer on site to oversee the operation, said Tampines Town Council.
The Building and Construction Authority (BCA) said the incident did not affect the structural integrity of the building. The dislodged structure is part of the building's exterior architectural facade.
"BCA has directed the building owner - Tampines Town Council - to engage a professional engineer (PE) to... carry out a detailed investigation and recommend permanent rectification works," a spokesman said in a statement.
"As an added safety precaution, the building owner's PE is also required to inspect all the other HDB blocks in the area with a similar architectural facade."
The Housing Board said its engineers are investigating the cause of the incident.
Tampines Town Council recently conducted painting and upgrading works in the precinct. It said last night that it will work closely with BCA and HDB in the investigation. It added that the area will be closed off until further notice.
"Town council officers will be conducting a visual inspection of blocks in the area over the next few days," it said. "We would also like to appeal to residents to inform the town council if they notice any cracks."
• Additional reporting by Annabeth Leow and Marcus Tan