Booking photos have been released of the four people arrested in connection with the disappearance of two Kansas women who were last seen driving through the Oklahoma Panhandle.

The Oklahoma State Bureau of Investigation announced that on Saturday, Tad Bert Cullum, 43, Tifany Machel Adams, 54, Cole Earl Twombly, 50, and Cora Twombly, 44, were taken into custody. All four were booked into the Texas County Jail on two counts of first-degree murder, two counts of kidnapping and one count of conspiracy to commit murder in the first degree, OSBI said in a press release.

Veronica Butler, 27, and Jilian Kelley, 39, were last seen on March 30 heading to pick up children before their car was found abandoned near the Oklahoma-Kansas border, with foul play suspected, police said.

Butler and Kelley have still not been located, OSBI said.

FBI JOINS SEARCH FOR MISSING KANSAS WOMEN IN OKLAHOMA

Tifany Machel Adams, 54, is reportedly the grandmother of Veronica Butler's children. (Oklahoma State Bureau of Investigation - Authorized Page/Facebook)

Tad Cullum, 43, is reportedly the boyfriend of 54-year-old Tifany Adams, who is the grandmother of Veronica Butler's children. (Oklahoma State Bureau of Investigation - Authorized Page/Facebook)

Cora Twombly, 44, is one of four arrested in the case of missing women Veronica Butler and Jilian Kelley. (Oklahoma State Bureau of Investigation - Authorized Page/Facebook)

Cole Twombly, 50, was arrested in connection with the disappearance case. (Oklahoma State Bureau of Investigation - Authorized Page/Facebook)

A missing persons advisory from the Texas County Sheriff’s Office says that Butler has "several tattoos, a Chinese symbol on her left forearm, a sunflower on her left shoulder" and that "Jilian has a butterfly tattoo on her left forearm."

The alert described Butler as being five feet, four inches tall with red hair and green eyes, last seen wearing a blue short-sleeve shirt and denim shorts.

YOUTUBERS SEARCH FOR MISSING KANSAS WOMEN INSIDE ABANDONED HOME: REPORT

Veronica Butler, left, and Jilian Kelley were last seen on March 30 while driving to pick up children, police say. (Oklahoma Highway Patrol)

Kelley has brown hair and blue eyes. She was last seen wearing a long-sleeve shirt, blue jeans and tan or beige shoes, the alert added.

The area near the Oklahoma-Kansas border where the vehicle the two women were traveling in was found abandoned, according to the Oklahoma State Bureau of Investigation. (Google Maps)

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OSBI is still investigating the case, along with assistance from the FBI and other local agencies.

OSBI public information manager Hunter McKee told Fox News Digital on Monday that "it’s becoming more and more challenging" to find the women alive as the days mount with no signs of their whereabouts.

Fox News' Greg Norman contributed to this report.

Mugshots released, revealing first look at suspects in case of missing Kansas women

Four suspects charged with first-degree murder in disappearances of Veronica Butler and Jilian Kelley