The US Customs and Border Protection (CBP) agency is reportedly detaining certain imports of Antminer series ASIC devices manufactured by Chinese company Bitmain at ports of entry into the country.

According to local press reports, at least seven US-based mining companies have reported that the Federal Communications Commission (FCC) has requested that CBP detain these shipments of ASIC miners at ports of entry.

The affected imports include Bitmain's latest and most advanced Antminer S21 and T21 miner models. These retentions do not appear to be directed at other ASIC manufacturers such as MicroBT or Canaan.

Mining industry sources said CBP has held up some of these shipments for two months, and delays are being seen nationwide , including at major ports such as San Francisco and Detroit.

So far, CBP has not provided a specific reason for these actions nor set a timeframe for the release of the shipments. This situation has caused confusion and concern among mining companies, as it is not a common practice in the industry.

Sources cited by Blockspace speculate that the hold could be related to Antminer control boards that use chips from Sophgo, a company that has been under scrutiny for allegedly violating US sanctions by supplying chips to Huawei.

This Chinese tech giant has been subject to sanctions since 2019 and shares a CEO, Micree Zhan, with Bitmain. After a Sophgo chip was discovered in a Huawei device, TSMC decided to cut business ties with Sophgo.

While there is no clear evidence to confirm that the import halt is specifically due to Sophgo scrutiny, it has been confirmed that Bitmain uses and even markets the Sophgo CV1835 chip in the Antminer T21 and certain models of the S19 series, including the S19k Pro, S19 XP, S19 Pro, and some S19j Pro models.

This board could be the reason for Bitmain's miner holdbacks. Source: Bitmain.

Since Sophgo may be under investigation by the US Department of Commerce, it is speculated that both the FCC and CBP are reviewing these shipments for the presence of these chips.

 However, Bitmain, like other ASIC miner manufacturers, sources control boards from multiple suppliers, suggesting that not all affected models necessarily contain the chip in question.

The ASIC miners seized by the US are considered to be among the most innovative and powerful on the market, which adds an additional level of impact to mining companies that rely on these technologies for their Bitcoin mining operations.