The truck apparently lost its brakes before slamming into a religious procession on Wednesday on the main road of Mazapil, a small town of 16,000 people in the state of Zacatecas.
Some 200 pilgrims were taking part in the event.
"We have 14 people killed at the scene and nine more at hospitals or while they were being taken there," a state civil protection official told AFP on condition of anonymity.
Officials had previously reported 16 deaths and 30 injuries.
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Local media showed pictures of the dump truck turned on its side. A red pick-up truck is stopped in front of it.
A police car and an ambulance had escorted the pilgrims during the procession, according to press reports.
Catholics have been taking part in a pilgrimage to the San Gregorio Magno church in Mazapil since Sunday as part of a celebration for a patron saint.