If you have a sentence whose construction is
[noun] [be-verb] [past participle]
it must be passive voice. Your two sentences are both passive voice: no context is required to determine this.
There is some possibility for confusion is a word can be either a past participle or an adjective, for example broken:
The window was broken on Thursday.
If broken is a past participle, this is passive voice: we are talking about somebody breaking the window on Thursday.
If broken is an adjective, the state of the window on Thursday was broken: it actually broke some time before that.
In such situations, context is required to identify the correct meaning.
Note that it is not necessary to specify an agent in a passive voice sentence. Indeed, one of the main reasons for using passive voice is that you don't know (or don't want to say) who the agent was, for example:
My car was stolen last night.
This phone was made in Korea
If you know who the agent is, and it is important for the sentence, you would normally use it as the subject in an active voice sentence:
That man stole my car!
You only use passive voice and specify the agent if the object/patient is the most important thing in the sentence, and the agent is of some lesser relevance to the story:
My husband was attacked by two youths last night.