地域 and 区域: a local region and a designated zone
Compare the region where a festival takes place with an area under construction, preserving the scope of the request concerning entry.
An event in a local region
地域（ちいき） means a region or local area. 「この地域では秋に大きな祭りがあります。」 says that this region has a large festival in the fall. 地域では identifies the region where the event takes place.
The sentence does not give the region's name or boundary lines. The presence of a festival does not define 地域 as an area divided only by natural terrain.
A designated area for the entry request
区域（くいき） means an area or zone. 「工事中の区域には入らないでください。」 asks people not to enter the area under construction. 工事中の specifies which area is meant.
入らないでください is a request not to enter. It does not state that someone already entered or that everyone complied, and it does not explain the conditions of an actual legal restriction.
Two ways of identifying an area
The festival example presents a local region in the context of an event. The construction example identifies a designated area to which the entry request applies. Size alone does not separate the words.
地域 is not limited to natural divisions, and 区域 is not limited to legally designated zones. The event and the designated area provide the relevant context.
Which area does 「工事中の区域には入らないでください。」 identify, and does it report an entry that already occurred?
Show the answer and why
It identifies the area under construction and asks people not to enter it. The sentence does not report an actual entry or the result of compliance.