DAYTON, Ohio (WDTN) — Crews have gone to historic measures in the search for missing seven-year-old Lucas Rosales, which included building a temporary dam on part of the Mad River to lower water levels.

Dayton fire chief Jeff Lykins said that is something that has never been done for a local missing person’s case.

This has been an expansive search, covering more than 400 acres in and around Eastwood MetroPark. Authorities have looked as far south as West Carrollton, searching both the Mad and Great Miami Rivers.

Crews have also used a variety of different methods to help locate Rosales. This has included using thermal and sonar image devices, K-9 units and different types of drones.

Chief Lykins said the temporary dam did help them access areas they previously were not able to search, but there is still no sign of Rosales.

Lykins also spoke to 2 NEWS about the most difficult part of the process that they’ve been dealing with from the very beginning.

“One of the difficulties with this particular incident was that we didn’t have a real good idea of the point last seen where the child may have fallen in,” Lykins said. “Obviously, that creates a difficulty when you’re trying to rapidly locate someone. So, we focused in that area, again, close proximity where the gentleman said he was fishing. There was a pond there, and then a leg of the river. So, those were our focus.”

Texas EquuSearch crews said they continue to hold out hope that they can find Lucas.