By Robin Rieger

MOORESTOWN, N.J. (CBS) - Two grown siblings who were sleeping upstairs in their Moorestown home Wednesday morning are lucky to have survived a fire that officials say started downstairs but spread to the attic.

Two good Samaritans, Tim Clements of Cinnaminson and his friend were passing the home on Flynn Avenue on their way to work around 8 a.m. when they saw the smoke and responded. Clements says they started banging on doors and windows to wake anyone inside. He says after ringing the doorbell and banging again, the brother opened the front door. Smoke he says was billowing behind him.

“My friend said, ‘You’ve got to get out of the house, it’s on fire,” said Clements.

The brother ran up to get his sister and they ran out of the home. Their parents were at work. The fire chief says the good Samaritans were there in the nick of time.

“It’s not fire that kills, it’s the smoke that kills. If they hadn’t woken him up, if he hadn’t gotten out in like a very short time, he’d have been done. We’d have had to go in a rescue them. Thank God that didn’t happen,” said Fire Chief Anthony Green.

The fire chief says the home has working smoke detectors. They went off after the occupants were woken up. The cause of the fire is under investigation.