1. An area or region that is currently being examined or inquired into by authorities, researchers, or officials
The contaminated area was declared a zone under investigation by environmental agencies.
A área contaminada foi declarada uma zona sob investigação pelas agências ambientais.
2. A geographical area where a criminal, scientific, or administrative inquiry is actively taking place
Police cordoned off the zone under investigation to preserve evidence.
A polícia isolou a zona sob investigação para preservar as evidências.