He said the police will investigate the case from every angle.
"Perhaps we will charge the father under the Child Act for negligence by leaving the child in the car with the engine still running," he told a media conference after attending a golf tournament with the Sabah Governor, in conjunction with the Sabah Police Contingent's 207th Police Day celebration, held at Nexus Resort Karambunai, here, Sunday.
The boy is believed to have been asleep in the rear seat of his father's four-wheel-drive when he was driven away, while his 31-year-old father, Low Yee Shang, stopped to go to the toilet at a petrol kiosk in Kg Air about 5.35am on Friday.
The vehicle was recovered several hours later near the Atkinson Clock Tower along Jalan Signal Hill, but the boy was nowhere in sight.
"How can you just leave your small child in the vehicle with the keys in its ignition," said Hamza.
He said police have conducted "Ops Tutup" in every exit and entry points, including bus terminals, jetties, Kota Kinabalu International Airport as well as the border with Sarawak as part of efforts to trace the boy.
"I have informed my men to be on the lookout but so far, there has been no further information," he added.
Meanwhile, police believe the manager of a caged-fish breeding company, who was kidnapped by a group of armed men in Pulau Baik, Lahad Datu last Tuesday, is still alive. Hamza said so far, no new arrests had been made and police assured that the case would be resolved.
"I wish to state that police would ensure security in Sabah and what happened lately were isolated cases (oil smuggling) and the kidnapping incident in Pulau Baik, which have given people the impression that security in Sabah is under threat, which is not true as we have reacted fast," he said.
On Saturday, Deputy Inspector-General of Police Datuk Seri Mohd Bakri Mohd Zinin was reported as saying that police had not received any demand for ransom money from the kidnappers.
Police are also still investigating the motive of the kidnapping.
In the incident about 2.45am last Tuesday, five armed men abducted the company manager, Yang Zai Lin, 34, who is from Guangzhou, China.