HUNDREDS of thousands of displaced Palestinians returning to their homes in northern Gaza have passed through checkpoints in a central zone of the enclave where scanners check for concealed weapons being taken in cars and vehicles.

Here is how the system works, according to witnesses who have passed through:

- The checks are run by Egyptian contractors with the help of a U.S. private security firm, although there have been no reports of U.S. citizens on the ground.

- Checkpoints appear to be staffed by Egyptian security personnel. Members of the inspection team wear black jackets marked "Egyptian-Qatari Committee".

- Armed uniformed Egyptian security personnel are also present, standing back from the main checking area.

- As the vehicles approach, all passengers get out, leaving only the driver in the vehicle, which passes into a drive-in inspection point where it is checked for weapons and explosives by a scanner.

- The whole process for each vehicle takes a few minutes, according to witnesses.

- Along the roads on either side of the checkpoint, in the so-called Netzarim corridor, Hamas police maintain order, while engineering units with sniffer dogs check the roadway for unexploded ordnance.