The death toll from a bus crash in South Africa on Friday has risen to 22, the authorities said.

Traffic officials initially reported that at least 10 people were killed when a double-decker bus crashed down an embankment into a valley, about 120 kilometers northeast of Cape Town.

The exact death toll could rise as some passengers were still trapped underneath the overturned bus, according to Western Cape traffic spokesman Kenny Africa.

Africa said rescuers were trying to use a crane to lift the bus or use tools to cut the wreckage so that the passengers underneath could escape.

Emergency service ER24 spokesperson, Vanessa Jackson, confirmed that eight people were critically injured and 36 had minor to moderate injuries.

He added that three passengers trapped under the bus had died

The bus, with about 80 people on board, crashed down the embankment in the Hex River Valley near the farming town of De Doorns.

The bus was en route to Cape Town from Johannesburg when the accident happened.

Africa said investigators suspected brake failure as the cause of the accident.

The accident took place when the Easter Holiday Road Safety campaign was in full swing in the country.

Authorities launched the campaign last week to reduce road carnages which claim more than 1 000 lives per month in South Africa, according to the Transport Ministry.

Road fatalities cost the country above 3 billion rand (about 333 million U.S. dollars) each year, according to Transport Minister Ben Dikobe Martins.

S.Africa has more than 700, 000 crashes a year on the average, with three children dying every day in road accidents, and the festive holidays usually have the highest rate of road deaths, according to the Road Traffic Management Corporation (RTMC). The RTMC has vowed to reduce the number of road casualties this year by 25 percent and achieve a 50-percent reduction in road accidents by 2020.