Four trucks were petrol bombed overnight in the Western Cape, with one of the drivers seriously injured in an attack near Porterville.Provincial traffic chief Kenny Africa confirmed that the driver has been admitted to the Piketberg Hospital for treatment, after he was attacked when he pulled off next to the N7 to sleep.At about 01:00, his truck was petrol bombed. The vehicle was destroyed by the fire and the driver was seriously injured.Africa said three other attacks had been reported between 21:50 and 02:00 on Tuesday morning.A truck driver was doused with petrol when his truck loaded with chickens was set alight at about 02:00 on the Piekenierskloof Pass.READ | N1 near Worcester closed after truck petrol-bombed"Petrol was thrown over the driver, but luckily he was not set alight and was unharmed," he said.At 00:30 on the N7 near Moorreesburg, a truck loaded with cement was petrol bombed and set alight after two vehicles forced it off the road, Africa said. The truck was gutted, but the driver escaped unscathed.On Monday night at 21:50, a truck was stoned and set alight on the N2 near Lwandle. "There were no injuries and the truck was empty at the time," Africa said.All the incidents were being investigated by police."Definite criminality" was behind the attacks, Africa believed, but the motive had not yet been confirmed.Traffic services would, together with the relevant authorities, try to establish a plan to curb the attacks, he said.