NEW : Official says Bluefin may be able to go deeper ; another vehicle that can awaits its call . Underwater probe will map ocean floor until 10 a.m . ET Wednesday , source says . Comment: Meanwhile , investigators are trying to determine significance of cell signal and oil slick .
NEW : Official says Bluefin may be able to go deeper ; another vehicle that can awaits its call . Underwater probe will map ocean floor until 10 a.m . ET Wednesday , source says . Vehicle 's first attempt ended early after it exceeded its maximum dive depth . Meanwhile , investigators are trying to determine significance of cell signal and oil slick .