(Updates death toll, quotes and details of rescue effort)
By Morade Azzouz
ROSNY-SOUS-BOIS, France, Aug 31 (Reuters) - A building in a Paris suburb collapsed after an explosion on Sunday morning, killing two children and two women, and teams were searching the rubble for four other people still missing by evening.
About 150 emergency workers worked throughout the day, some using sniffer dogs, to try to find four adults still unaccounted for, said the prefect of Saint-Seine-Denis, Philippe Galli.
"The later it gets, the more remote the possibility of finding survivors," said Galli.
"Nevertheless, we still hope to find in a pocket someone who managed to find a way to protect themselves."
An 8-year-old child was the first victim to be found dead after the explosion at around 7 a.m. (0500 GMT), followed by the discovery of an unconscious 80-year-old woman in the debris. She died while being taken out, fire department spokesman Gabriel Plus said.
Later in the afternoon, a woman in her 40s was found dead followed by the body of her child, Galli said.
Eleven people were injured in the incident, some of them seriously.
Interior Minister Bernard Cazeneuve, speaking to reporters at the scene, said the explosion appeared to have been caused by a gas leak.
"We should be prudent, because there are investigations ongoing. There is no certainty," he said.
One side of the four-storey building in the suburb of Rosny-Sous-Bois was ripped off completely, exposing the interiors of apartments. Local authorities said the structure appeared to have conformed to building codes.
A rescue mission could last up to 48 hours, authorities said.
Local residents who rushed to help in the moments after the blast described a bloody scene.
"We tried to take people out," said Arafet Brahim, who said he and his friends pulled out some children who appeared to be in good shape.
"But we also took bodies out," he said. "Frankly it was horrible, I don't know how to describe that moment," he said. (Writing and additional reporting by Alexandria Sage; Editing by Andrew Roche)