Body found in burnt out Sydney store

A body has been found in the rubble of a shop fire in Sydney's inner west.

The body has not been identified and its gender is not known.

It was discovered at around 4.30pm on Thursday in the remains of the convenience store in Rozelle which was destroyed by an explosion in the early hours of the morning.

Three hours later, police said the body could not be retrieved because the site is still too unsafe.

Three residents of the building, Bianka O'Brien, her 12-month-old son Jude and a 30-year-old male neighbour were unaccounted for after the blaze.

"It was a painstaking brick by brick removal," said Inspector Clive Ainley, the commander of the Leichhardt local area command.

"We're still optimistic, it's still a rescue mission, we're still optimistic we can find survivors."

The explosion is being treated as suspicious.

"At this stage, it's an arson," Insp Ainley said.

"It's too early to speculate whether it's a homicide."