Officials say 16-year-old Shaina Nicole Tenney and her seven-month-old daughter Grace had been abducted by Shaina's step-father, Margel Tenney.
Police say they were traveling on Interstate 79 in Ohio. They were taken from a house in Rock Cave, in Upshur County.
Margel, the alleged kidnapper, is 57-years-old. Police said on Tuesday the children were believed to be in extreme danger.
Margel Tenney is charged with sexual abuse by a guardian, with more charges to follow.