Search efforts for a missing Chattanooga boy and his step-grandmother have expanded to include a boat and a drone.

Family members identified the missing hikers as 14-year-old Jackson Standefer and his step-grandmother.

Chief Ranger at the Grand Canyon National Park, Matt Vandzura, said the drone will be used to get to some of the more remote areas.

He described some of the terrain near Tapeats Creek where the hikers were last seen on Saturday.

"The land on either side varies from flat, sandy, relatively level areas to steep-sided, inaccessible gorges," Chief Ranger Matt Vandzura said.

Officials with the National Park Service said the two hikers were crossing the creek when they lost their footing and were swept away.

Jackson's mother and his step-grandfather were also hiking with them.

They used what's called a personal locator beacon, which alerts search and rescue resources. Family members can also be notified when it's activated.

Nearly two dozen people are searching for the teen and his step-grandmother in the Grand Canyon National Park. This is the third day crews have been looking for them. 

Standefer's uncle, Mark McOmie, wrote the following public Facebook post:

"The outlook is not promising, but there is still a glimmer of hope. We will hold on to this hope until there is reason not to. Please keep praying."

Vandzura said the group of hikers are experienced. Officials with the Grand Canyon National Park said they conduct more than 200 search and rescue missions a year, but this case is different.

"The bulk of our search and rescue missions, we know where the patient, the person is. Truly searching for people is relatively rare," Vandzura said.

Standefer is an 8th grade student at The McCallie School. McCallie's Deputy Director of Communications and Marketing, Jim Tanner, released the following statement to Channel 3 on Monday:

"As has been reported by several media outlets, McCallie eighth-grader Jackson Standefer has been missing in the Grand Canyon since late Saturday on a family trip. 

Jackson and his step-grandmother were swept downstream while attempting to cross a river Saturday afternoon. Rescue efforts began quickly and are ongoing. The family remains hopeful that rescuers will find Jackson and his step-grandmother and return them safely to their families.

This morning, students were told about the situation involving Jackson and the ongoing rescue operations and hopes for rescue. The boys have been offered help if they need it as they process this situation.

The entire McCallie community sends its prayers to the Standefer family and all those close to Jackson as we all hope for a positive ending to this situation. Out of respect for the family, McCallie will not be making faculty or students available for further comment at this time."