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

Yes

The word "investiguei" is identical in spelling, grammar, and meaning in both Brazilian and Continental Portuguese. The only difference lies in pronunciation. Brazilian Portuguese tends to have more open and "musical" vowels, making the unstressed syllables clearer. In Continental Portuguese, vowels are often more closed or "reduced," meaning unstressed vowels (like the "e" in the middle of the word) may be pronounced very softly or almost swallowed.

Brazilian Portuguese Examples

1. Investiguei o celular dele. (I investigated his cell phone.)
2. Investiguei o ônibus para ver se algo estava errado. (I investigated the bus to see if something was wrong.)
3. Investiguei o trem antes de embarcar. (I investigated the train before boarding.)
4. Investiguei a galera toda no evento. (I investigated the whole gang/group at the event.)
5. Investiguei o estacionamento do shopping. (I investigated the shopping mall parking lot.)

Continental Portuguese Examples

1. Investiguei o telemóvel dele. (I investigated his mobile phone.)
2. Investiguei o autocarro para ver se algo estava errado. (I investigated the bus to see if something was wrong.)
3. Investiguei o comboio antes de embarcar. (I investigated the train before boarding.)
4. Investiguei a malta toda no evento. (I investigated the whole group/crowd at the event.)
5. Investiguei o parque de estacionamento do centro comercial. (I investigated the shopping mall parking lot.)