The rain, poor maintenance, adding cars to the train because of the road closure, trying to make up the delay adding cars could all be part of the causes for this tragedy.
News reports with pictures:
http://thenewsnigeria.com.ng/2016/10/cameroon-train-crash-death-toll-tops-70/
http://www.telegraph.co.uk/news/2016/10/21/cameroon-train-crash-dozens-dead-after-packed-passenger-train-d/
Quote
Scottish Daily Record and Sunday Mail
The inter-city passenger train was travelling from Yaounde to the commercial capital, Douala, when the accident occurred around 11am (10am GMT).
"There was a loud noise. I looked back and the wagons behind us left the rails and started rolling over and over. There was a lot of smoke," said a Reuters journalist travelling in a wagon near the front of the train.
He said that, before its departure from Yaounde, a railway employee said additional wagons had been added to the train to accommodate extra passengers, though it was unclear if that played a role in the accident.
The collapse of a bridge along the main highway between the capital and Douala had prompted increased numbers of passengers to undertake the journey by rail.
BN