This is the dramatic moment a mother forgot her baby as her home's ceiling roof collapsed - before running back to save him with a split-second to spare.

The shopkeeper Pip Srey had closed for the day and was holding her baby while two other youngsters and her toddler in a stroller was with her in Phnom Penh, Cambodia, on July 3.

She suddenly heard a rumble and crack from overhead as she turned on her heels and fled, along with the boy and girl. However, she had forgotten about the boy, named Bong, in the stroller.

Heartstopping CCTV footage shows how heroic mum Pip ran back into room and grabbed the toddler moments before the ceiling collapsed. She managed to pull him to safety as her husband emerged at the door.

Pip said: 'He would have died if the roof fell on him. It was just my instinct to run away when I saw the roof falling down. Something made me look back and I saw him there so I just ran over and grabbed him.'

Builders were called in to repair the shophouse-style home close to a market along Veng Sreng Boulevard in the capital city.

They blamed 'poor construction' and recent heavy rain that had weakened the building. The roof has since been replaced with stronger materials and LED strip lighting.

The builder said: 'There was no water-proofing in the original plans for the house. All of the rain has made the ceiling weaker. It is because of poor construction.

'People should be aware of this when they buy homes, as one day it could fall down, just like what happened here.'