When considering bags held by people in the photos, we need to keep in mind that the pressure cookers, filled with nails and ball bearings, would be rather heavy and would distend the backpack. From this photo, these bags fit the bill.
In the second photo, the one in the blue adidas jacket still has his bag, and we can see the strap across his right shoulder. The guy in the white hat does not have his bag on his back. However, from the position of his arms he may have the bag at his feet. The other spectators, including his colleague, are looking at the runners, while the guy in the white hat is looking straight forward. Is he looking for a spot to leave his backpack? Of does he have his eyes closed, and is he saying something? Hard to tell.
The one in the adidas track suit jacket looks to me Algerian, or at least Maghrebi. He does have the build of a bona fide distance runner, and of course there are outstanding middle and long-distance runners from that region.
Does anyone think the guy in the white hat looks anything at all like the at-large al-Qaeda terrorist Adnan Gulshair el Shukrijumah?
This seems worth raising the question. If these guys are just bystanders, hopefully they will contact LEO and identify themselves so they can be removed from those investigated.