TOKYO, Dec 19 (Reuters) - Japan's Nikkei share average edged down on Tuesday morning in choppy trade, as construction stocks extended a punishing sell-off on growing concerns some of the firms may have breached antitrust regulations.
The Nikkei was flat at 22,905.40 in midmorning trade, after opening up 0.3 percent.
The construction sector slipped 1.5 percent and was the worst performer on the board, after Tokyo prosecutors raided Japanese construction companies on suspicion of antitrust breaches related to $80 billion worth of magnetic levitation (maglev) train line projects.
Taisei Corp, one of the so-called "big four" group of Japanese construction firms involved in the maglev project, was the latest to be raided. Its shares tumbled 5.3 percent to more than a three-month low.
Peers Shimizu Corp and Kajima Corp were raided on Monday also on suspicion of antitrust breaches related to the projects. Obayashi Corp is already under investigation for suspected bid-rigging over maglev-related contracts. Shimizu dropped 3.0 percent, Kajima shed 5.4 percent, while Obayashi declined 1.6 percent. While the scope of the probe has broadened the scale of the suspected wrongdoing remained unknown and prosecutors declined to comment.
Brokerage stocks outperformed, with Nomura Holdings gaining 1.1 percent and Daiwa Securities rising 1.3 percent.
The broader Topix shed 0.1 percent to 1,815.86. (Reporting by Ayai Tomisawa; Editing by Shri Navaratnam)