Is the sentence "X is located in Y" active or passive voice?

Locate is a transitive verb and so can form a passive. The active

The three travellers located the source of the river 50 miles inland.

becomes, in the passive,

The source of the river was located by the three travellers 50 miles inland.

However, in the construction X is located in Y, the -ed form of the verb is a participial adjective acting as the complement of the verb be. The question of voice does not arise. No one, I imagine, would think of sentences such as I am tired, This problem is complicated or They were very pleased as being any kind of passive. So it is with sentences like Paris is located in France and The key was located in the second drawer on the left.

EDIT:

Huddleston and Pullum, authors of ‘The Cambridge Grammar of the English Language’ distinguish between the ‘adjectival passive’ and the ‘be-passive’. In the sentence ‘Paris is located in France’, ‘located’ is the former, but the sentence ‘The source of the river was located by the three travellers’ is the latter. They point out that the difference is that when the verb preceding an adjectival passive is ‘be’, it can be substituted by another verb. So, we can say ‘Paris remains located in France’, but in the second sentence, there is no alternative to ‘was’.

The Oxford Dictionary of English Grammar refers to this kind of construction as "pseudo-passive", i.e., it ".. neither has an active counterpart nor permits an agent." It contrasts pseudo-passives (which it also calls statal passives), where the verb to be is "arguably a copular verb," with true passives (actional passives), which can be converted to an active form with the agent as the subject.

Here's a good primer on the passive by Geoffrey Pullum, a contributor to Language Log and co-author of The Cambridge Grammar Of The English Language.