Authorities in Guatemala are investigating the horrific crash involving a passenger bus with 70 people on board outside Guatemala City, after it plowed through a safety guardrail, plunging 115 feet into a polluted ravine early Monday morning.

At least 56 people are dead after a bus plunged off a bridge Monday on the outskirts of Guatemala's capital, Guatemala City Fire Department spokesman Carlos Hernández told CBS News.

At least 54 people were killed after a bus veered off a bridge into a ravine in Guatemala City on Monday, according to the country’s National Institute of Forensic Sciences.