Police repeatedly told Susan Cox-Powell’s parents in recent months that the arrest of her husband, Josh Powell, in connection with her disappearance was imminent, a family attorney said Tuesday.

“My clients were assured repeatedly by the West Valley Police Department that an arrest was pending, be patient,” attorney Steve Downing said on HLN’s “Nancy Grace.” “…They were told repeatedly that something was going to happen and it never did.”

Downing said Chuck and Judy Cox were told last year that Powell would be arrested by November 15, and when that didn’t happen, they were told the arrest was coming sometime this summer. He said police were “absolutely” aware that Powell’s children had made statements about their mother being in a mine or in the trunk of a car - and one had even drawn a picture of the family van with Susan in the trunk - but they still did not act.

“Assurances after assurances, the arrest never happened,” family attorney Anne Bremner told Grace.

When asked about Downing's allegations, West Valley Police Sgt. Mike Powell told HLN that “Anything specific to our actual investigation itself we are not able to release or discuss at this point. We still have an active missing person investigation and the integrity of that investigation is of the utmost importance to us.”

Susan Cox-Powell was reported missing on December 7, 2009. Josh Powell told police at the time that he took their two sons camping in the middle of the night and Susan was gone when they returned. Police have called him a suspect in her disappearance and he lost custody of the children last fall.

In a voicemail message obtained by ABC News, Powell reportedly told family members Sunday he could not live without his sons. About 20 minutes later, authorities believe he attacked the boys with a hatchet during a court-ordered visit and set his house on fire, killing all three of them.

For the latest on the Powell family tragedy, watch “Nancy Grace” tonight at 8 p.m. and 10 p.m. EST on HLN.

• A voicemail Powell recorded before killing two boys and himself: 'I am not able to live without my sons'

• Authorities say boys suffered hatchet wounds before death

• Attorney says son drew picture of missing mom in trunk

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An attorney for the parents of missing Utah mother, Susan Cox Powell, said the woman’s children whose bodies were discovered Sunday in a fatal home explosion recently started talking about the night their mother vanished.

The attorney, Steve Downing, said the oldest boy recalled his mother being in the trunk.

“Charlie had been asked along with other members of [his] class to draw a picture of something they did in summer,” Downing said. “At some point he drew a picture of the family van. The dad was driving the van, he and his brother were in the backseat and mom was in the trunk.”

Susan Powell's sister Denise Cox told HLN’s Nancy Grace that the boys were increasingly able to verbalize what they remembered.

"Actually, the boys at first when my parents received custody of them they didn't talk that much," Denise Cox said, "but over the last few months they started opening up and talking to my parents about what happened that night and my parents would relay it back to me."

Cox said Josh Powell did not permit the boys to talk about their mother or to mention her name.

The bodies of the two children, Charles, 7, and Braden, 5, were found in their father Josh Powell's Pallyup, Wa. Home, after he allegedly ignited the explosive blast during a court-ordered visitation.

Police say Josh Powell, who had been named a person of interest in the disappearance and suspected murder of his wife Susan Cox Powell, was also killed in the blast along with the boys.

Firefighters who responded to the scene found the Powell home engulfed in flames and nearly charred to its frame. The bodies were discovered in the living room. The blast shook nearby homes, rattled windows and spewed debris onto lawns located blocks away.

A social worker who brought the Powell boys to Josh Powell's home Sunday reportedly told police that Powell let the boys inside, then blocked her from entering and locked the door. The social worker reportedly pounded on the door and immediately contacted supervisors to report the incident. She reportedly told supervisors she noticed the smell of gas outside the home.

The home exploded moments later. The social worker was not injured.

According to police, Josh Powell sent e-mails to multiple people confirming that he planned the deadly blast. Jeffrey Bassett, the attorney who had been handling Powell's child custody case says he too received an e-mail from his client minutes before the explosion saying "I'm sorry, goodbye."

Police say the blast was fueled using accelerants spread throughout the home.

Josh Powell allegedly told police he took his two boys, then ages 2 and 4, on a Sunday night camping trip. Powell told police he returned home that Monday evening in December 2009 to find his wife missing.

Powell was never charged in connection with his wife's disappearance, but lost custody of their children after his father Steve Powell was arrested on charges of child pornography and voyeurism. The boys had been living with their maternal grandparents.

Denise Cox speculates that Josh Powell drugged his sister before her death.

"I believe he drugged her so it didn't seem unnatural for the boys when he took her," she said.

"I believe he told them that they were going to go look for mines and I believe he buried her somewhere out wherever he went."

Cox said from what she gathers from her parents, the Powell boys had been talking about how their mother went into a mine to look for crystals and never came out.

Autopsies on the three bodies are scheduled Monday.

Police continue to investigate the disappearance of Susan Cox Powell.

For more on this story tune into Nancy Grace tonight on HLN, 8pm EST and go to HLNtv.com FULL POST