This spot is just next to the truck, close to the gate leading out of the map, and can trip you up if you're not aware of it.
This check is on the same side of the bridge, directly opposite the first check.
Directly in the middle of the bridge.
This check is on the left, if you're coming from the bridge.
Inside the building to the right, in the room directly in front of you.
Outside that same building, in the alleyway behind it, hidden behind some crates.