(a) close inquiry
inquire [go] into 《a matter》 closely
investigate 《a matter》 thoroughly
【形式ばった表現】 carry out a thorough investigation 《of an incident》
読み方 ついきゅう
Close inquiry; thorough investigation:(=する) to inquire into (a matter) closely; to investigate (a matter) thoroughly; to probe (a matter) to the bottom