There was a suggestion made regarding rewarding fishermen for finding pieces of debris.
How about going one further? Supposedly they have video of the two (or more?) passengers flying with the stolen passports. How about publishing their photos, and offering a reward to anyone who can identify them?
If they were non-terrorists simply attempting to immigrate, then most likely they had family members or friends who knew it. Even if they were smugglers, someone might well recognize them who knew what they were involved in.
Identifying the men and ruling out (or ruling in) their possible link to terrorism could help to narrow in on what actually happened.