Authorities are searching for two hikers from Vermont who are missing in rugged terrain in Badlands National Park in South Dakota.

The Pennington County Sheriff's Office says the 23- and 24-year-old women texted a friend Wednesday night saying they were lost. Authorities suspended the search about 2 a.m. Thursday and resumed it around four hours later.

Sheriff's spokeswoman Patty Garland says terrain in the area is hilly with trees and knee-high wild grasses that are difficult to walk through. Garland says it is easy for hikers to become lost if they wander off established trails. There are wild animals in the area, including bison.

Authorities haven't released the women's names. The sheriff's office says the hikers left their vehicle and camping equipment at a campground in the park.