An overcrowded bus has plunged into a deep river canyon in northwestern Guatemala, killing at least 44 people who had been travelling to the capital.

Grieving families gathered outside a recreation centre near the accident site where authorities set up an improvised morgue to identify the bodies of the passengers, including children and at least three babies.

The spokesman for the volunteer fire department, Mario Cruz, said 46 people were taken to regional hospitals for treatment of injuries.

Marcos Rene Zet, 17, was crying outside the centre as medical personnel performed post-mortems on the corpses. He said he couldn't believe he had lost his mother, two sisters and three nephews.

"My mother told me she was going to the capital to buy food. She sells food outside schools," Marcos said as he waited for news.

The fire department spokesman said approximately 90 people were aboard the Guatemala City-bound bus, which had an official capacity of 54 passengers.

The bus driver, Yony Cumar Cana, died in the accident.

"Some of the people were rescued with hydraulic equipment, and others were thrown (from the bus) at the time of the accident," Mr Cruz said.

People from the nearby town of San Martín Jilotepeque gathered at the scene and were shocked when they saw rescue workers carrying out the bodies of three babies wrapped in pastel-coloured blankets.

Boys and girls were brought out of the canyon on stretchers.

The bus ended up in the river at the bottom of the 600ft (200m) canyon at around 8.15am, apparently after the driver lost control on a bend.

Twisted metal from the bus was scattered in the ravine.

"From what we see, the bus crashed against a wall of rocks first and then fell over the cliff," said mayor Otto Vielman.

The area has mostly dirt roads that wind through steep mountains without guardrails or other safety measures.

The mayor said a similar bus accident in 2000 on the same road killed 40 people.