At least 43 people, including newborn babies, have died after a bus plunged 200 metres (660ft) into a ravine in northwestern Guatemala.

Rescue workers said the overcrowded bus veered off a road in in San Martin Jilotepeque, roughly 37 miles (60km) northwest from the capital Guatemala City.

At least 40 more people are believed to have been injured in the crash, which completely destroyed the bus. It had been traveling to San Martin Jilotepeque from Chimaltenango.

The cause of the accident is not yet known. Rescue workers said conditions were sunny and dry at the time of the crash. A fire department spokesman said 90 people were aboard the bus, which only had a capacity of 54.

Forty people were reportedly confirmed dead at the scene, with a further three more at the hospital. At least three of the dead included babies, the fire department spokesperson added.

President Otto Perez declared three days of official mourning in the wake of the tragedy.

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

A similar bus crash on the same road killed 40 people in 2000, Vielman added.

Guatemala is the fifth-worst country in Latin America in terms of road accidents, with 20 in 100,000 inhabitants killed in crashes in the Central American nation.