Netz, judging by the current routine, you can tell, that they stick the RFID in the direction they go just after the turning point. There was an RFID to the right (east direction), and just after you found another to the left this time (north direction). This is also by your senses the only possible way, but judging by the time difference (there were 10 minutes delay, on somthing you covered in just three or four, they could be debating, and/or inspecting other tunnels before going further.