The situation has grown more desperate by the hour in Venezuela as people dig through the rubble of collapsed homes and flat blocks three days after the devastating one-two punch of 7.2 and 7.5-magnitude earthquakes, knowing time is running out to find survivors.

Authorities announced on Friday night that they would block access to La Guaira, the epicentre of the destruction, as chaos and traffic began to hamper search efforts. Officials said anyone who wanted to enter would now have to seek official permits, but provided few details of who would be allowed in.

Venezuelans took the search for missing loved ones into their own hands, citing a scarcity of government rescuers, as the human toll of Wednesday’s quakes climbed to at least 920 dead and more than 51,000 missing. People reported seeing few state rescue teams in the hardest-hit areas, despite authorities projecting an image of a robust government response.

Aid agencies consider the first 48 to 72 hours to be a crucial time frame to retrieve people alive, though that can be extended if they have access to food and water.

“Each person saved is a miracle,” said Jorge Rodriguez, president of the National Assembly. “We are not going to hide absolutely anything about the magnitude of this tragedy.”

In the state of La Guaira, just north of the capital, Caracas, Nazareth Jimenez sobbed into a loved one’s shoulder as she watched neighbours use hammers and power tools to try to cut through slabs of concrete in a building reduced to a mountain of debris. She was wracked with anxiety as she waited to see if her siblings, nephews, nieces and friends would emerge alive.