1-Some men who might be involved with the crime syndicate are being held for questioning.
The way I see thing there are three distinct possibilities:
a-Maybe they are all involved
b-Maybe some are involved
c-Maybe none is involved
I feel there is some ambiguity in 1, in that it is not clear if we are talking about the involvement of those men as a group or about the involvement of those men as distinct individuals.
2-A group of men who might be involved with the crime syndicate is being held for questioning.
I think here we have two distinct possibilities:
d-Maybe the group is involved
e-Maybe the group is not involved
But if the verb is changed from 'is' to 'are', we will still have the same ambiguity as in '1'.
Is that correct?