BOGOTA - At least 11 people were killed and 33 others injured early Saturday in a bus accident on a highway in Central Colombia's Caldas province.

The bus from the city of Quibdo was heading to the Colombian capital Bogota when the accident happened. The bus lost control on a dangerous curve and crashed into a hill, according to the commander of the Highway Police, General Francisco Patino.

The authorities are investigating if excess speed is the main reason to have caused the accident.

"It is regrettable that 11 people were killed in this incident," said the officer, offering his condolences to the families of the victims.

Nine people were killed on the spot and their bodies were taken to the city of Fresno, which is nearest to the accident site. Two more passengers died in the hospital of Manizales city, capital of Caldas province.

According to initial reports, the bus conductor has driven 12 hours at the time of the accident.

"We are investigating about the journey and whether driver had taken rests (...) whether licenses and vehicle documents are up to date," Patino said.

Most of the 33 injured are hospitalized in Manizales' care centers, including the bus conductor and his assistant. Some bus passengers told local media that the automobile was stranded three times before the accident.

This is the most serious accident recorded in Colombian national roads since the start of the holiday season.