The houses were so badly damaged that emergency repairs were necessary to make them safe for investigators to get inside.
Two people in the plane and two children in a home were killed.
Thirteen-year-old-old Sade Brantley and 1-year-old Madisyn Mitchell were killed when the plane hit their home, setting it on fire.
Also killed were the pilot, 54-year-old former Microsoft executive Bill Henningsgaard, and his 17-year-old son, Maxwell.
The 10-seat propeller-driven plane crashed on its approach to Tweed New Haven Airport.
The NTSB is expected to issue a preliminary report on the crash in the next two weeks.