It's still stuck in their facility. Ask the sender to check with them for this item.

It may be a valuable good, that is why it's being detained. My goods are also being detained. No worries, they just want you to declare it in front of them. You may not need to pay tax if they do not ask you to. Otherwise, they just want to see only.

Just go to the Pusat Mel & Kurier Pos Malaysia, next to LCCT Sepang.

Another thing is sometimes USPS tracking number cannot be used at their website because POS Malaysia will somehow issue another tracking number for their system, that will only be available to us when their letter of detained good by customs arrive at our doorstep. The best and most effective way, however, I recommend, is to:

(This is in accordance with USPS tracking website.)

1. Wait till your parcel has ARRIVED AT SORT FACILITY in MALAYSIA.
2. Once arrived, it should be sent for CUSTOMS CLEARANCE.
3. Within the same day or next day, if all is good it should show CUSTOMS CLEARANCE PROCESSING COMPLETE.
4a. Once customs finish processing it, it SHOULD be delivered to you within 5 working days by Pos Malaysia to your provided address.
4b. However, if customs clearance status is stuck for max. 3 days, you should call up the customs in Pos Malaysia KLIA to double check with your parcel providing them your USPS tracking number.

This is just a simple guide for you to understand a little better about USPS, because we all don't like waiting. But at certain times USPS may delay their parcel shipment to Malaysia because our parcels go on transits too. But a few more things that I am able to clarify that is:

i. The guide above is probably for certain type of parcels only! The features that my parcel had was International Parcels.
ii. If your parcel is stucked at PROCESSED THROUGH SORT FACILITY in USPS ISC Facility (max. 2 weeks), you may need to call up your sender to ask them to check with USPS for your parcel. It may still be stucked/delayed in their facility, like I mentioned that USPS may delay it due to transits.
iii. Last but not least, the phone number to check your parcel or "boom" Pos Malaysia is 03-87773777.
iv. The location of Pos Malaysia KLIA is just right next to LCCT. Go towards LCCT and look for Pusat Mel & Kurier Pos Malaysia. You may need to go their to collect your parcel if your parcel is being detained by customs or for different reasons.

Hope this helps to clarify things for all users of USPS. But again, there is always risks with international parcels. So choose wisely with couriers.