"We began to look at Michael Powell much more closely at that point," the deputy police chief said.
Police brought cadaver dogs to the place where Michael Powell's car had been impounded. While the car had not been crushed, according to the deputy police chief, only the frame and the structure of the vehicle remained.
"The dogs did indicate the odor of human decomposition [in the car]," said Deputy Police Chief Powell. "We were able to extract a minimal amount of DNA from the trunk of that vehicle."
While investigators could not obtain "a full profile" from the sample, they concluded the DNA did not match the profile of Susan Powell. Still, it made authorities interested in her husband's brother.
As the investigation progressed, Powell said police found a significant amount of communication between Josh and Michael Powell that had been encrypted via the Internet.
In February, a year after his brother killed himself and his sons, Michael Powell committed suicide by jumping from a Minneapolis parking garage.
"We looked into him as completely and thoroughly as we possibly could," Deputy Police Chief Powell said. "I can tell you that he was involved in some capacity in the disappearance of Susan. There is a high probability that he had a direct involvement."
ABC News' Colleen Curry and Kevin Dolak contributed to this story.