Taiwan is investigating four firms whether they broke US sanctions or its own investment rules when they provided services to Chinese companies that are reportedly helping Huawei build chip factories, media reports said.

Emile Chang, a Ministry of Economic Affairs official in charge of reviewing investments, told CNN Friday that an “administrative probe” had been initiated this week into four Taiwanese companies named in a media report.

The investigation will focus on whether their business activities in China were consistent with approvals they had been granted by the ministry, he said.

If any of them are found to have violated the rules, each company is subject to a maximum fine of 25 million New Taiwan dollars ($777,000), reports CNN.

The ministry will also look into whether the companies — Topco Scientific, United Integrated Services, L&K Engineering Co and Cica-Huntek Chemical Technology — violated any US sanctions, Chang added.

All four companies deny any wrongdoing. In separate statements, they said they were involved only in wastewater management, interior decoration or construction work approved by Taiwan, and did not provide semiconductor materials or equipment, the American news channel reported.

Huawei has emerged as a symbol of tech rivalry between the USA and China.

The USA and its allies have sought to curb its access to advanced chips and chipmaking technology due to fears that Huawei spies for the Chinese government.

The Chinese tech firm has always denied the allegations.

Beijing perceives self-ruled Taiwan as an integral part of China.

Taiwan considers itself to be an independent nation.