3 sentences

1. 他在公安局从事刑侦工作。

   tā zài gōng'ān​jú cóng​shì xíng​zhēn gōng​zuò.

   He works in criminal investigation at the public security bureau.

   Source: Dong Chinese Dictionary

2. 如果你丢了护照，应该立即去公安局报案。

   rú​guǒ nǐ diū le hù​zhào, yīng​gāi lì​jí qù gōng'ān​jú bào'àn.

   If you lose your passport, you should report it to the public security bureau immediately.

   Source: Dong Chinese Dictionary

3. 由于护照快过期了，我明天得去公安局办证。

   yóu​yú hù​zhào kuài guò​qī le, wǒ míng​tiān děi qù gōng'ān​jú bàn​zhèng.

   Since my passport is about to expire, I have to go to the Public Security Bureau tomorrow to handle the paperwork.

   Source: Dong Chinese Dictionary