For your question, we would like to have below suggestion.

Note: Our answer is for your reference only, not legally obligated.

* About holding package:

     Pursuant  to Article 15 Chapter 3 of Customs law dated June 29, 2001on Principles for carrying out customs procedures, conducting customs inspection and supervision:

 “Exported, imported and transited goods, transport means on exit, entry or in transit must go through customs procedures, be subject to customs inspection and supervision, transported along the routes and through the border gates prescribed by law”

      Pursuant  to Article 24 Chapter 3 of Customs law dated June 29, 2001on responsibility to inspect goods and transport means within the geographical areas of customs operation

- Within the geographical areas of customs operation, the customs offices shall have the responsibility to inspect export and import goods, and transport means on exit or entry.

- For goods and transport means which are, as prescribed by law, subject to specialized quality, medical, cultural inspection or animal and plant quarantine, the State bodies with specialized inspection competence shall conduct the inspection thereof.

* About time of delivering items:

Goods and transport means shall enjoy customs clearance after the customs procedures have been completed.( Article 25 Chapter 3 of Customs law dated June 29, 2001)

Therefore, your package may be in the customs inspection or specialized test process. You should contact directly with Customs Post Office where your items is being held to be more specific guidance.