(h) A copy of the petition shall be served in any manner provided by law for service of process or complaint in an action in assumpsit on the owner if he can be found within the Commonwealth. If the owner cannot be found within the Commonwealth, a copy of the petition shall be served on the owner by registered mail or certified mail, return receipt requested, addressed to the last known address of the owner. The person in possession and all encumbrance holders having a perfected security interest in the property confiscated shall be notified in a like manner. The copies shall have endorsed thereon a notice substantially similar to the following: "To the claimant of the within property: You are required to file an answer to this petition setting forth your title in and right to possession of said property, within twenty days from the service hereof, and you are also notified that if you fail to file said answer, a decree of forfeiture will be entered against said property."