By Shawn Nottingham and Hollie Silverman, CNN

The search for a missing hiker on Hawaii's Big Island is in its second week, while another hiker in Maui has been missing since July.

Kyle Brittain was last seen August 30 on the trail near Waipio Valley lookout, according to a news release from the Hawaii Police Department.

He told his family he was going for a hike on the transverse trail in Waipio Valley towards Waimanu Valley, the release said.

His father, Steve Brittain, told CNN affiliate KHON that someone saw the missing hiker near a bathroom at the Waipio Valley overlook.

"He asked where the bathroom was and said, 'Hey have a good day,' and that was the last time," Steve Brittain told the affiliate.

He said his son's phone also pinged on the mountain around 8:30 a.m. on Friday before losing service, KHON reported.

Since then, search and rescue teams have trekked throughout steep and dangerous terrain looking for the missing 27-year-old from Hilo.

The police search for Brittain ended after five days, his sister-in-law Heather Lee, said.

Members of the search team that found missing hiker Amanda Eller are helping search for Brittain, according to Lee.

She thinks he is still alive and can find fruit and water in the wilderness as he awaits rescue.

Javier Cantellops told CNN by phone Sunday night that he and four teams were out searching in steep terrain and marshy areas with rough water.

Cantellops said about 30 volunteers are searching for Brittain, KHON reported.

Brittain's family has also flown in search dogs and is growing concerned about how long he's been missing, KHON reported.

"Unfortunately, we're starting to look for things we don't want to look for because it's been a week so we're starting to look in the rivers and the swamps," Brittain told KHON.

"It's been a long week, and you know the crying stopped this morning for a while and it will come back."

As rescuers try to find Brittain on the Big Island, the search for another hiker continues on Maui.

Khiara Henry, 23, of San Diego, California, was last seen on July 21 when she rented a car in Kahului, according to a news release from August 5 from the Maui Police Department.

Her vehicle was later found at the Waianapanapa Park area but she has not yet been located, the release said.

Police said they received several leads on Henry's case but were not able to confirm any of them.

New surveillance footage of Henry from the car rental office was released by officials Friday, according to KHON.

Her family has offered a $10,000 cash reward for the first tip leading to Henry's safe return and/or the arrest of the person or persons responsible for her disappearance, KHON reported.

CORRECTION: An earlier version of this article gave the wrong day Khiara Henry was last seen. It was July 21.