Is the word investigaram the same in Brazilian and European Portuguese?

Yes

The only difference between the two dialects regarding this word is phonetic. In Brazilian Portuguese, the pronunciation is more "open" and syllabic, meaning the vowels are clearly articulated. In Continental Portuguese, the pronunciation is more "closed" or "consonantal" due to vowel reduction; unstressed vowels (like the "i" at the beginning or the "a" in the middle) are often shortened or nearly swallowed, making the word sound much more clipped. The spelling, grammar, meaning, and usage are identical.

Brazilian Portuguese

1. Os policiais investigaram o roubo. (The police investigated the robbery.)
2. Os cientistas investigaram a nova vacina. (The scientists investigated the new vaccine.)
3. Os alunos investigaram o tema do projeto. (The students investigated the project theme.)
4. Os detetives investigaram a pista. (The detectives investigated the clue.)
5. Os jornalistas investigaram a fraude. (The journalists investigated the fraud.)

Continental Portuguese

1. Os polícias investigaram o roubo. (The police investigated the robbery.)
2. Os investigadores investigaram a nova vacina. (The researchers investigated the new vaccine.)
3. Os estudantes investigaram o tema do projeto. (The students investigated the project theme.)
4. Os detetives investigaram a pista. (The detectives investigated the clue.)
5. Os jornalistas investigaram a fraude. (The journalists investigated the fraud.)