Active voice is when the subject of the sentence performs the verb’s action. Joe aims the gun. Martin reads the book.

Passive voice is when the subject is acted upon by the verb.

The gun is aimed by Joe. The book is read by Martin. It nearly always contains a “by X” phrase.

There, now go do your homework.

Security sources said that they used six to eight kilos of explosive material in the device and they have recovered parts of suspected suicide bell.

Hope it helps!

This site tells you how to change from passive to active voice. I have a hard time explaining it, but the site will be able to do that for me. Good luck!