TOKYO (AP) — China's stock market fell sharply Friday as investigations into the securities industry widened to include two top brokerages. Most other Asian markets were lower in muted trading after Wall Street was closed for the Thanksgiving holiday, and investors continued to watch for developments in tense relations between Russia and Turkey. Japan's benchmark Nikkei 225 retreated 0.3 percent to 19,883.94 and South Korea's Kospi fell 0.1 percent at 2,028.99. Two major Chinese brokerages announced they are under investigation for possible violation of securities market rules in the latest aftershock of this summer's market plunge. Markets have been wary about geopolitical tensions after Turkey downed a Russian plane that entered its territory from war torn Syria.