A 42-year-old man from Qormi was injured on Thursday when the truck he was sitting in was hit by a compactor at the Magħtab waste dump.
The compactor was being driven by a 64-year-old from the Philippines, the police said.
The accident happened at around 2.45 pm.
He was given first aid on the spot before being taken to Mater Dei Hospital, where his condition was found to be serious.