The Securities and Exchange Commission is expanding its informal investigation of companies that it claims have been offering to executives stock option grants backdated to when share prices were low so that their recipients can profit from them in the future. The Wall Street Journal reports the list of companies allegedly involved continues to grow, with six new ones added late last week, including UnitedHealth, Trident Microsystems, Juniper Networks, Affiliated Computer Services and Vitesse Semiconductor Corp. According to the paper, 10 executives or directors at some of the targeted companies – though not necessarily the ones mentioned above – left their positions recently.