boston boston mayor martin walsh former labor leader say monday federal agents contact connection local media describe wide-ranging investigation whether city build unions use strong-arm tactics boston globe report weekend cite unnamed source walsh implicate federal investigation whether city union officials threaten developers hire nonunion workers project around city contact walsh tell reporters monday democrat walsh former construction worker lead city build construction trade council union group two years 2013 mayoral election victory walsh serve state representative 1997 2013 go say even investigation former union concern investigation assume point indictments come case get one walsh say nothing wrong spokeswoman u.s. attorney office boston could reach immediate comment boston mayor say subject federal probe labor unions