Hannah was seen in a car with DiMaggio about 20 hours before he allegedly set fire to his house, police said Tuesday.
The two were seen in DiMaggio's blue Nissan Versa just after midnight Sunday, August 4, said San Diego County Sheriff's Department spokeswoman Jan Caldwell. She confirmed reporting from the Los Angeles Times that the two were spotted at a U.S. Border Patrol checkpoint.
Caldwell did not say what the two were doing together, or if Hannah Anderson was with DiMaggio voluntarily.
CNN was unable to get an Anderson family response to this revelation.
Actions raise eyebrows
Some of Hannah's actions have raised eyebrows in some quarters.
A friend of Hannah's told authorities "DiMaggio took her on multiple day trips," according to a search warrant.
The same document said phone records indicate the two "called each other approximately 13 times" shortly before both their phones were turned off around 4 p.m. (7 p.m. ET) on August 4.
That was around the time that Hannah was picked up from cheerleading practice at Sweetwater High School, the warrant says, while noting it wasn't known who picked her up.
The same document says that a fire was reported at around 8 p.m. later that day at DiMaggio's two-story log cabin and a detached garage in Boulevard, California.
After battling the fire, authorities found the bodies of the teenager's mother, Christina Anderson, and Ethan.
An affidavit claimed that both had been "tortured and killed" by DiMaggio, who then set his home and garage ablaze.
A fire captain found Christina Anderson face down in the garage, covered with a tarp, and with a crowbar and what appeared to be blood next to her head.
An Amber Alert was issued the next day.
The ordeal ended about 1,000 miles from where it started, on August 10, when an FBI tactical agent shot and killed DiMaggio in the Frank Church-River of No Return Wilderness, about 15 miles outside Cascade, Idaho.
As to Hannah, she was physically unharmed and soon returned to her family in Southern California.
The teenager hasn't spoken publicly or with reporters since the ordeal. But she did field anonymous questions on the website ask.fm, according to Alan MacNabb, whose son is one of Hannah's closest friends.
In those comments, she said DiMaggio had apparently set some kind of a timing device to start the blaze at his home. She also said she did not want to go with her "dad's best friend" and that, had she tried to escape from him, "He would have killed me."