"We support investment in Germany but we must make sure that there is no outflow of technology," the source told Reuters.

"The activities of Chinese investors have increased. We are intensively watching these developments."

A growing number of Chinese companies are seeking to acquire key German industrial technology.

Last week, home appliance maker Midea Group made a $5-billion bid for German robot maker Kuka, while on Monday China's Fujian Grand Chip Investment Fund LP agreed to buy Aixtron for 670 million euros (510 million pounds).

ChemChina has also set its sights on SGL Carbon, according to a report from Manager Magazin.

(Reporting by Markus Wacket; Writing by Caroline Copley; Editing by Joseph Nasr)

Stocks treated in this article : KUKA AG, SGL Carbon SE, AIXTRON SE