A method of electronic article surveillance, EAS, comprising: - in a radio frequency identification, RFID, system comprising a plurality of non-co-located interrogation antennas (202, 216; 502a, 502b), each antenna being independently controllable by the system to interrogate one or more of a plurality of target zones one target zone at a time for a presence of RFID tags of the system in each interrogated target zone: - first interrogating, by the system in a first mode, one or more particular target zones of the plurality of target zones including a given target zone, each particular target zone being interrogated with one of the antennas (202, 216; 502a, 502b) at a time at a first power for the particular target zone; - monitoring, by the system upon first interrogating, for a trigger condition to occur; - in response to the trigger condition not occurring, continuing, by the system , the first interrogation in the first mode; characterised by - in response to the trigger condition occurring, second interrogating, by the system , the given target zone in a second mode at a second power with a plurality of the antennas (202, 216; 502a, 502b) at a same time in synchronization, wherein the second power for the given target zone is greater in aggregate across the second interrogating antennas (202, 216; 502a, 502b) than the first power for the given target zone. - in a radio frequency identification, RFID, system comprising a plurality of non-co-located interrogation antennas (202, 216; 502a, 502b), each antenna being independently controllable by the system to interrogate one or more of a plurality of target zones one target zone at a time for a presence of RFID tags of the system in each interrogated target zone: - first interrogating, by the system in a first mode, one or more particular target zones of the plurality of target zones including a given target zone, each particular target zone being interrogated with one of the antennas (202, 216; 502a, 502b) at a time at a first power for the particular target zone; - monitoring, by the system upon first interrogating, for a trigger condition to occur; - in response to the trigger condition not occurring, continuing, by the system , the first interrogation in the first mode; characterised by - in response to the trigger condition occurring, second interrogating, by the system , the given target zone in a second mode at a second power with a plurality of the antennas (202, 216; 502a, 502b) at a same time in synchronization, wherein the second power for the given target zone is greater in aggregate across the second interrogating antennas (202, 216; 502a, 502b) than the first power for the given target zone. - first interrogating, by the system in a first mode, one or more particular target zones of the plurality of target zones including a given target zone, each particular target zone being interrogated with one of the antennas (202, 216; 502a, 502b) at a time at a first power for the particular target zone; - monitoring, by the system upon first interrogating, for a trigger condition to occur; - in response to the trigger condition not occurring, continuing, by the system , the first interrogation in the first mode; characterised by - in response to the trigger condition occurring, second interrogating, by the system , the given target zone in a second mode at a second power with a plurality of the antennas (202, 216; 502a, 502b) at a same time in synchronization, wherein the second power for the given target zone is greater in aggregate across the second interrogating antennas (202, 216; 502a, 502b) than the first power for the given target zone. <EOS>