Two young women hiking in Alaska's Denali National Park remained missing Tuesday, as searchers stepped up their efforts to find them.

Abby Flantz, 25, of Gaylord, Minn., and 23-year-old Erica Nelson of Las Vegas were supposed to be on a short backpacking trip through the preserve, but haven't been seen since last week.

Nelson was due to be on a plane Sunday night to fly to Houston and be the maid of honor in her sister's wedding, said park spokeswoman Kris Fister.

"It’s a hard thing for the families to have to deal with at this time," Flantz family friend Rod Tollefson told FOX News on Tuesday.

The women may have had trouble crossing a raging river in the park.

They were last seen Thursday at the Savage River check station about 15 miles from Denali headquarters. They had planned to return Friday.

Flantz and Nelson were reported overdue on Saturday when they did not show up for work at a hotel outside the park.

Ground and air crews have searched nearly 100 square miles of the nearly 9,400-square-mile preserve.

Searchers camped out Monday night, about three miles from where the women were last seen Thursday, according to Fister.

Tollefson said foul play wasn't suspected.

"That was brought up, but really they don’t consider that to be an issue at this point," he told FOX. "There’s no evidence of anything like that."

The Associated Press contributed to this report.