Investigators are focusing on a lake behind the house in which 7-week-old Aniston Walker was last seen.
Armstrong says they are also using cadaver dogs and searching a Memphis landfill.
Police officers were also seen at the East Memphis apartment of Tramond Chitman, 33.
Investigators are still working to put together a timeline for when the baby was last seen and when she went missing.
They say Aniston's mother, Andrea Walker, 33, is not being as forthcoming as they hoped. Armstrong said she is a suspect. (WMC-TV) – Memphis police have charged Andrea Walker, 33, with two counts of Aggravated Child Abuse and two counts of Aggravated Child Neglect or Endangerment. Walker was booked at 4:06 a.m. on Friday. AuthoritiesMore >> According to the affidavit of complaint, Andrea Walker, 33, left her 7-week-old baby, Aniston, and a 3-year-old home alone while she took her 5-year-old son to school.
(WMC-TV) - The Memphis Police Department issued a City Watch Alert for a 7-week-old child Thursday. Aniston Walker was last seen at 5604 Falling Bark Drive in Bartlett. He has brown eyes and weighs aboutMore >> Aniston Walker was last seen at 5604 Falling Bark Drive in Memphis, which is just outside of Bartlett.More >>
Click here to see photos from the search for 7-week-old Aniston Walker.More >> Click here to see photos from the search for 7-week-old Aniston Walker.More >>