LA GUAIRA, Venezuela — Venezuelans took the search for missing loved ones into their own hands Friday in the aftermath of back-to-back earthquakes, saying they have seen few state rescue teams in the hardest-hit areas despite authorities projecting an image of a robust government response.

The apparent lack of government help compounded families’ desperation as the pressure to find buried survivors increased with each passing hour. The South American nation on Friday marked nearly two days since the disaster. Aid agencies consider the first 48 to 72 hours to be a crucial time frame to retrieve people alive, though that period increases if they have access to food and water.

Meanwhile, a broad international aid effort accelerated, with more than two dozen rescue teams from around the globe arriving in Venezuela or due to arrive there soon.

The toll from the devastating 7.2 and 7.5 magnitude quakes that struck late Wednesday climbed to at least 920 dead and 3,360 injured, authorities said.

“Each person saved is a miracle,” said Jorge Rodríguez, the president of the country’s National Assembly.

Desperate families across northern Venezuela searched in the ruins of buildings for family members and whatever remained of their lives.

Nazareth Jimenez sobbed into the shoulder of a loved one as she watched neighbors try to cut through slabs of concrete with hammers and power tools in a building reduced to a mountain of debris. “My god, how are we going to get them out of there?” she murmured.

She was in the northern state of La Guaira, just north of the capital of Caracas, where some of the worst destruction unfolded. Jimenez was wracked with anxiety as she waited to see if her siblings, nephews, nieces and friends would emerge from the debris alive.