The people spoke to the AP on condition of anonymity because the workouts have remained private and the Dolphins haven't talked publicly about negotiations.
Early Friday morning, Broncos executive John Elway was seen at the Centennial, Colo., airport. The same plane that picked up Manning for a session with Denver last week was en route to the Raleigh-Durham area, where Manning has been rehabilitating from neck surgeries.
Duke coach and longtime Manning friend David Cutcliffe told The Tennessean that Manning has made good progress throwing the football.
AP Sports Writers Steve Wine in Miami and Pat Graham in Denver contributed to this report.