The final photos of a grandmother and her step-grandson have been posted after they went missing in the Grand Canyon. Photo/Mark McOmie Facebook

Chilling final images of a grandmother and her step-grandson have been posted after the teen's GoPro was recovered by search and rescue.

Lou-Ann Merrell, 62, and Jackson Standefer, 14, were hiking in the Grand Canyon on Saturday, April 15 when the pair lost their footing while trying to cross a creek during a family trip in a remote part of the northern Arizona park. They were swept away by the water.

An intense search was then initiated for the pair, which included three ground teams consisting of about 20 people total, a National Park Service helicopter, a drone and an inflatable motor raft that was flown into the canyon.

The search and rescue eventually discovered a backpack, with a GoPro mounted on it which carried the last photos of the two of them.

The boy's uncle, Mark McOmie, has now posted the tragic final photos recovered from the GoPro, which show the pair smiling and enjoying their time with family.

But the search in Grand Canyon National Park has since been scaled back, with a park spokeswoman saying the searchers on the ground won't be used because they've now checked all areas that they can reach on foot.

The search will continue with the helicopter, drone and motorised inflatable raft.

A statement released by the hikers' families thanked the searchers and said the families "are still praying for a miracle in Grand Canyon National Park" but support the decision to scale back the search.

"After carefully considering all the information available to us, and based on our personal knowledge of the search area, we support Grand Canyon National Park's ... decision to scale back the search," the statement said.

Both hikers are related to Randy Merrell, the co-founder of the Merrell Boot Co., a popular outdoor footwear maker.

The missing grandmother is the wife of Randy Merrell and she was with her husband, step-grandson and the boy's mother on a multi-day hike when she and the boy lost their footing.

he Grand Canyon is consistently one of the most popular attractions in the United States, drawing nearly 6 million people last year.

But the park's nearly 2,000 square miles, steep cliffs and mesmerising views have often led to accidents and deaths.

The park service reported over 1,000 medical emergencies, 15 deaths and 318 search and rescue incidents in 2015, the last readily available data. The remote area where the family was hiking is at the bottom of the canyon near the North Rim, a much-less visited area of the park.

- With AP