The news director of an Iowa-based NBC affiliate said Thursday that the station would turn over footage of its interview with the mother of one of two missing cousins after authorities served a subpoena that claimed it could help their investigation.

Waterloo-based KWWL-TV announced Wednesday night that it received the subpoena seeking "raw video" of interviews conducted last week with Misty Morrissey and Wylma Cook and made the document public on its website.

News director Dan Schillinger said Thursday the station was in the process of giving authorities its full interview with Misty Morrissey, which has been available on its website. Cook was standing next to Morrissey during the interview, but she didn't speak. The station does not have any additional footage because its policy is to get rid of outtakes, Schillinger said.

"I think they are trying to leave no stone unturned," he said of investigators.

The subpoena application, filed Monday by Black Hawk County Attorney Thomas Ferguson, says the footage is needed so his office can conduct a "complete investigation" into the disappearance of 10-year-old Lyric Cook and 8-year-old Elizabeth Collins.

The girls disappeared July 13 after taking a bike ride in Evansdale while their grandmother, Wylma Cook, was babysitting them. An extensive search involving local, state and federal investigators has failed to find them.

Authorities classified the case as abduction after a search by divers using sonar equipment ruled out the possibility their bodies might be recovered in an Evansdale near where their bikes were found. Investigators have focused attention on Lyric's parents, Daniel and Misty Morrissey, who have a long history of being involved in drugs, but have not called them suspects.

The July 20 interview with Misty Morrissey being sought by authorities came days after the family said she had stopped cooperating with investigators or speaking to the news media, citing an attorney's advice.

During the interview, Morrissey told KWWL-TV reporter John Wilmer that she and her estranged husband sought legal advice after they were accused during lengthy interrogations of having involvement in the girls' disappearance. With her mother, Wylma Cook, standing next to her, she called it a "pretty intense coercion" and said the scrutiny was probably the result of her criminal record.

"They don't have anything else. We've been to a briefing last night. There's no other information, no new leads, no evidence, there's nothing," she said. "After seven days, I realize it's probably very frustrating for them that they probably haven't been able to come up with something. It's frustrating for us as well."

Ferguson said investigators sought the footage at a time when Misty Morrissey had stopped cooperating with them. On Monday, she resumed talking to investigators and took a second polygraph test.

"Law enforcement wants to be aware of what it is they are commenting or talking about, especially in situations where they had publicly indicated they were not going to be cooperative," he said.

KWWL — whose letters stand for "Keep Watching Waterloo" — has aggressively covered the case. Its veteran 10 p.m. anchor, Ron Steele, beat other reporters by an hour on July 20 by tweeting news that an FBI dive team had not found the girls' bodies in the lake. Its live interview earlier that day with Misty Morrissey also was seen as a scoop.

Schillinger said the story has "occupied the lion's share of our resources" for nearly two weeks. He said crews were at Meyers Lake almost nonstop for several days, and have been working long days in the summer heat to bring its viewers the latest information.

"We hope for a positive resolution," he said. "We hope the girls are found and that they are safe and sound and we're doing everything we can to help."