You have to investigate into this affair.

你必须深入调查这件事。

The principal promised to investigate into that affair.

校长答应去调查那件事情。

The principal promised to investigate into that affair.

校长答应调查那件事情。

OK, you make a report, and we'll investigate into this case right away.

好的，你写一份报告，我们会立刻调查这件事情。

OBJECTIVE to investigate into the production technique of Kangjue Injection.

目的研究抗厥注射液生产工艺。