In seeking to verify the reports, federal agents have culled Mateen’s electronic devices, including a laptop computer and cellphone, as well as electronic communications of those who made the claims, law enforcement officials said.

So far, they have found no photographs, no text messages, no smartphone apps, no gay pornography and no cell-tower location data to suggest that Mateen — who was twice married to women and had a young son — conducted a secret gay life, the officials said.