KNOXVILLE, Tenn. (WATE) — After nine days of searching and more than 300 tips, crews still have not found 5-year-old Summer Wells, and the terrain is only making the search harder.

Emergency search crews from 106 agencies across Tennessee and five other states have searched 4.6 square miles, that’s a little over 3,000 acres. Search operations have been slowed by the mountain terrain as the conditions are exhausting crews both mentally and physically. Additional resources from the local, state and federal level are being used to bring in fresh eyes and rested bodies to the search.

“Search efforts will continue on a more specialized team basis throughout the rest of the week. Just because you may not see us in a large presence, once again rest assured we are still out here searching for Summer Wells,” incident commander of ground search Captain Tim Coup of the Church Hill Rescue Squad said. “We will not quit until we find Summer Wells.”

The Tennessee Bureau of Investigation says teams were conducting line searches Thursday in the Beech Creek community where Summer was last seen. They’re trying to comb through every inch of ground – especially overgrown areas and fields with high grass.

In addition, officials are continuously urging people to search for a child hiding on their property. Coup says Wells “could hide in an area that a legal size piece of paper or folded up laptop could go.”

Different teams are searching through areas multiple times to make sure that nothing is missed. Coup says some of the areas have been covered as many as six times, “new ground, same ground, different eyes, fresh body … one flat-looking field, there’s a 100 places (Wells) could hide.”