[gore_sux]

Looks like they are scouring the same area in this pic.

[Wayne07]

Another angle:

[matt1234]

The bomb may have been placed in the tree well.

The picture above (and at post 56) shows 2 investigators kneeling next to a "tree well." A tree well is a gap in a concrete sidewalk that allows a tree to grow. In this case the gap is rectangular. The well is commonly covered with a steel grate (at sidewalk level) with empty space below to allow for drainage. In this case, a rectagular grate is in two sections. One section has been removed and is on the sidewalk behind the right-hand kneeling investigator. The other section is still in place.

Many tree wells contain drainage pipes, electical junction cavities, or other crevices that could contain a bomb.

[Alberta's Child]

When I see where they are looking in that photo, I'm wondering if the bomb wasn't planted underground next to the tree.