Rosa Lopez told reporters that four of her nieces and nephews were thought to have been on the bus.
“When we heard about the accident on the news, we headed straight here,” the 48-year-old said.
Injured passengers were taken to hospitals, many of them in serious condition.
Guatemalan President Bernardo Arevalo expressed sorrow over the tragedy and declared a three-day period of national mourning.
“Today is a difficult day for the Guatemalan nation,” he said.
Murky waters
The fire department said the driver apparently lost control of the bus and collided with several small vehicles before plunging over the precipice.
“The bus kept going, broke through a metal railing, and fell into a ravine about 20 meters (65 feet) deep until it reached the sewage-contaminated river,” the department’s Carlos Hernandez told reporters.
AFPTV images showed lines of firefighters passing bodies pulled from the murky waters, which were filled with trash, up the slope on stretchers.
“We’re having a hard time with the rescue work,” said firefighter Luis Quintanilla.
“We’ve been underwater for more than three hours trying to rescue the body of an apparently male person who is trapped between the twisted metal of the bus,” he said.
The bus was traveling to Guatemala City from the town of San Agustin Acasaguastlan in El Progreso department, about 90 kilometers (56 miles) to the northeast, authorities said.
“It’s a huge tragedy, very painful,” 40-year-old Marbelin Ortiz, a resident of the area near the accident site, told reporters.
