HONG KONG (AP) — Taiwan authorities are investigating four Taiwan-based companies suspected of helping China’s Huawei Technologies to build semiconductor facilities.

Minister of Economic Affairs Wang Mei-hua said Friday that the investigation will determine if the companies have violated regulations prohibiting sales of sensitive technologies and equipment to China.

The Ministry of Economic Affairs summoned the semiconductor and factory services suppliers for questioning after a report by Bloomberg said they were working with Huawei as it builds a network of computer chip plants.

The investigation also will study whether the companies exported any any sensitive technologies or products with military applications that are included in Taiwan’s list of Strategic High-Tech Commodities, Taiwan’s China News Agency and other reports said.

They said semiconductor material reseller Topco Scientific Co.; cleanroom constructor L&K Engineering Co.; construction and design firm United Integrated Services Co. and chemical supply system provider Cica-Huntek Chemical Technology Taiwan Co. were suspected of supplying equipment or services to Huawei.

The companies could be fined up to 25 million Taiwan dollars ($777,665) for violating regulations.

Cleanrooms and other high-tech equipment and services are crucial for the delicate process of making computer chips.

The four companies did not immediately respond to requests for comment.

Wang said Taiwan’s National Science and Technology Council soon plans to announce a list of key technologies that require control measures to prevent sharing semiconductor techology with China. The government will take into consideration national security and technical considerations in deciding what measures to impose, she said.

Earlier this week, Wang said during a hearing in Taiwan’s Legislative Yuan that the four companies only provided low-end factory services, such as wastewater treatment and environmental protection and did not provide any critical services to Huawei, the reports said.

But Wang reminded companies that if they used U.S. technology and equipment they would not be able to co-operate with firms included in the U.S. Entity List, which prohibits companies from doing business with a listed company unless they obtain a license to do so.

Huawei was placed on the U.S. Commerce Department’s entity list in 2019. U.S. officials say the company is a security risk and might facilitate Chinese spying, an accusation that Huawei denies.