But by late Thursday, no evidence had emerged that Mr. Farook had communicated with anyone of “significant investigative concern,” one official said, and no evidence that he was tied to, or inspired by, any terrorist group.

The officials spoke on the condition of anonymity because they were not authorized to discuss an investigation publicly.

Dozens of investigators, some of them operating out of armored vehicles,congregated at the couple’s townhouse, moving slowly for fear of explosives. They picked through the dwelling overnight and through the day Thursday, and also scoured a Nissan sedan parked at the curb. They considered ordering neighbors to evacuate, but then told them to shelter in place, setting up a cordon to keep everyone else at a distance.

The authorities collected several electronic devices from the home, including a computer, cellphones, a music player and thumb drives. Law enforcement officials said they had begun reviewing Mr. Farook’s emails, while other items were being sent to the F.B.I.’s investigative laboratories in Quantico, Va., where analysts will scour them for information.