At least 37 people have been killed in a multiple pile-up in Peru when a bus drifted into the opposite lane.

According to an Associated Press article, the number of injured people, which was originally reported as 70, is now up to 84.

The bus was operated by the Murga Serrano line, and was transporting a group of evangelicals from Worldwide Missionary Movement, a Christian organization.

In total, the bus was hit by three vehicles -- two buses and a truck -- that were coming in the opposite direction.

The deadly road accident occurred in the pre-dawn hours at the Pan American Highway near Huarmey, which is approximately 200 miles north of the Peruvian capital of Lima.

On Monday, police chief Gen. Jorge Flores, according to Al Jazeera, has said that the most seriously injured of the crash victims were transported via helicopter to Lima from the scene in Huarmey, which is about 321km north of the capital.

As reported by Reuters, Oscar Gonzalez, the man who was in charge of the rescue operation, said that the "Initial investigations indicate that the driver who drifted into the opposite lane may have fallen asleep and collided with another bus."

As reported by the Associated Press, the survivors of the crash told their local media that it took emergency crews about three hours to get to the scene.

The Peruvian government sent five medical specialists to Huarmey to assist the small clinic there in caring for the injured.

Road traffic accidents are a common occurrence in Peru.

The World Health Organization has noted that there were 2,514 deaths reported on Peruvian roads in 2010.

This latest accident is the country's most serious crash since October 2013. In that accident, 51 people perished in a makeshift bus that had fallen into a ravine.