BELOIT, Wis. (AP) -- A woman who pretended to be pregnant stole her half-sister's newborn boy from a Wisconsin home and left him in a storage crate outside an Iowa gas station in frigid temperatures as police closed in, according to court documents filed Friday.

Federal prosecutors in Madison charged Kristen Smith, of Denver, with kidnapping Friday afternoon, hours after an Iowa police chief miraculously discovered Kayden Powell, who is nearly a week old, alive and well in the plastic storage crate that morning.

The discovery of the infant shortly after 10 a.m. Friday capped a frantic search that involved scores of police officers in Wisconsin, Illinois and Iowa.

"He's strong," the newborn's great-uncle, Mark Bennett, said of the boy. "I'm glad that baby is still living instead of in a ditch somewhere on a strange highway."

Online court records didn't list Smith's case or a defense attorney Friday evening. She faces life in prison if convicted.