Taiwan's National Communications Commission (NCC) revealed the preliminary findings of its investigation during a legislative session on Thursday. The regulator has been examining the phones since August to see if they met local security requirements.
The investigation has so far found problems with 12 phone models, said the commission's vice chairman Yu Hsiao-Cheng during the legislative session. "Almost every one of them will register with their company's server," he added, without elaborating on the specific issues.
Both Apple and Xiaomi were named, but on Friday the commission declined to list which other vendors were being probed.
The investigation was brought up after local legislator Chiu Chih-Wei pointed to security concerns with Xiaomi, a handset maker based in neighboring mainland China. The company's Android smartphones have become popular in Asia, but the devices have drawn scrutiny for sending customer data back to company servers without users' permission.
In August, Xiaomi apologized for causing the privacy issues, and made changes to the phone's software.
On Thursday, however, Chiu asked why Taiwan's local mobile carriers were still selling Xiaomi phones, given the alleged privacy risks. "Because there are no restrictions, the government could end up using Xiaomi phones," he said.
In response, Taiwan's NCC said during the legislative session that the privacy problems extend to other brands including Apple.
Both Apple and Xiaomi did not immediately respond to a request for comment. In October, Xiaomi said it was moving customer data of its international services to servers outside of China. A month earlier, Apple CEO Tim Cook explained the company's privacy policies in an open letter.
Taiwan's NCC is still completing its investigation, and will release the results some time later, said a commission official on Friday.