An outsized rally in Volkswagen shares has drawn the attention of Germany’s top market watchdog as heavy-volume trading spurred by the carmaker’ electric vehicle ambitions sent the stock rising as much as 32% this week. Shares in Volkswagen AG reversed course on Thursday, however, after hitting their highest level since April 2015 as regulator BaFin said it was monitoring the share price move and a buying frenzy from the United States appeared to cool down. A spokeswoman said BaFin was watching the move in a “routine way,” without elaborating. A raft of announcements on its electric vehicle expansion strategy to challenge market leader Tesla Inc has lifted Volkswagen shares more than 50% so far this year, luring institutional and retail investors globally. Momentum in the share price grew on Monday after the 83-year-old group unveiled it would build 12 battery cell plants in Europe by 2030 and expand charging infrastructure for electric cars.