The smoldering remains of a house, left, where an explosion killed Josh Powell and his two sons, Sunday, Feb. 5, 2012, is shown from the air in Graham, Wash. The explosion occurred moments after a Child Protective Services worker brought the two boys to the home for a supervised visit. Powell's wife Susan went reportedly missing from their West Valley City, Utah, home in December 2009. (AP Photo/Ted S. Warren)

Police released 911 calls that revealed a social worker's frantic attempts to alert authorities that Josh Powell had locked himself in his home with his two young sons, moments before he set off a huge fire that killed all inside.

"He exploded the house!" the social worker tells an operator at one point.

Before the fire erupted, the woman, who was supposed to monitor a supervised visit between Powell and his children, said he grabbed them and wouldn't let her in the door.

"What should I do?" she asks the operator. "Nothing like this has ever happened before at these visitations. ... I could hear one of the kids crying, and he still wouldn't let me in."

Josh Powell let the boys in the house, then blocked the social worker from entering. The social worker called her supervisors to report that she could smell gas and called 911.

Listen to CPS worker calls 911 (full call) from Josh Powell's drive

There is confusion at the beginning of the call, and it continues until the very end, when the social worker asks how long it will be before help arrives.

Case worker: How long will it be?
Operator: I don't know ma'am. They have to respond to emergency, life threatening situations first. The first available deputy ...
Case worker: Well this could be life threatening. He went to court on Wednesday and he didn't get his kids back. And this is really ... I'm afraid for their lives.
Operator: Has he threatened the lives of the children previously?
Case worker: I have no idea.
Operator: We'll have the first available deputy contact you.

Read the full 911 call transcription

The operator didn't yet know how serious the situation had become.

The explosion in the 8100 block of 189th Street Court East occurred moments after the two boys, 5-year-old Braden and 7-year-old Charles, were pulled inside.

The case worker called 911 again after the home exploded.

"People are saying there is not somebody here, but I was just there, and there is somebody here! There is two little boys in the house."

Listen to CPS worker call 911 after home explodes

Josh Powell's sister also called 911 after receiving a goodbye email from her brother. Filled with emotion she tells the operator that she received other emails from her brother earlier in the day that seemed "weird."

The operator asks her if it's the Josh that has been in the media.

"Yeah, the one that's been being abused by everyone," she replies.

Listen to Powell's sister's 911 call

When the Powell home fire exploded, one neighbor called because he could see it from his own home.

The operator asked if anyone was home, but the neighbor didn't know.

Listen to Powell neighbor calls 911

Pierce County Detective Ed Troyer told 97.3 KIRO FM's Ron & Don Show that investigators have determined Josh Powell's plot to kill himself and his two young sons goes back at least 24 hours.

Listen to Detective Ed Troyer

Police released the grizzly autopsy results of Charles and Braden on Monday.

Officers continued their investigation Tuesday, searching a storage unit that belonged to Josh Powell.

It now appears that Josh Powell may not have been living in the Graham house that he set on fire Sunday, and may have only staged it for visitations.

In his Graham neighborhood, Troyer said neighbors rarely saw people coming and going from the house that Josh Powell was renting.

"We think he was living in places where he shouldn't have been. But he'd just staged a home with pictures on the wall of Susan and some of the kids clothing there, just enough stuff for the visitation. The neighbors never saw him," Troyer said. "So we think he was just using the house as a staged location for visitations."

As police worked Tuesday, trying to determine why Powell ultimately committed the murder-suicide, questions remain about the status of the investigation into his wife's 2009 Utah disappearance.

For at least six months, Utah authorities have investigated the disappearance of Susan Powell as a murder case. But without a body, they publicly held out hope that she would be found alive.

Salt Lake County District Attorney Sim Gill acknowledged for the first time that investigators believe Susan Powell is likely dead, but he said in an interview with the Associated Press that the case remains a missing persons probe for now.

West Valley, Utah, Police Chief Buzz Nielsen said despite the death of the young boys and Josh Powell, the probe would continue.

"Our case is not closed," the police chief said.

A funeral for Charlie and Braden Powell has been scheduled for Saturday.

You might also be interested in:

Ross & Burbank: 911 call "most frustrating conversation"
Funeral for Charlie, Braden Powell planned for Saturday
Autopsies: Josh Powell's sons suffered chop injuries
Timeline of events in Powell case

The Associated Press contributed to this report.

MyNorthwest.com, Staff report