Prosecutors in Germany have arrested three German citizens for allegedly obtaining technologies for China’s secret service that could be used for military purposes.

The prosecutors on Monday said one of the suspects acted as an agent for an employee of China’s Ministry of State Security, and that this suspect used a couple who runs a company in Germany.

The prosecutors said that the couple concluded a cooperation agreement with a German university through their firm. They said its aim was to prepare a study for a Chinese contractual partner on machine parts that are also important for engines in ships, including warships.

A local media outlet quoted officials familiar with the investigation as saying German university officials were unaware of the three people working for the Chinese intelligence service.

The prosecutors said that at the time of their arrest, the suspects were in negotiations for further research projects that could be useful for expanding China’s naval combat power.

German Interior Minister Nancy Faeser said in a statement on Monday that she is aware of a significant danger posed by Chinese espionage in business, industry and science.