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 a dispatcher 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 dispatcher. “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.”Also Tuesday, police searched a storage unit Powell rented as they tried to determine why he ultimately committed the murder-suicide, and questions remained 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.What evidence did they have that the 28-year-old mother of two was dead? And was there anything to identify her killer? There was the damp spot on the floor in the Powells’ Utah home and a curious late-night camping trip described by Josh Powell. There were also the recollections of their young son Braden about a camping trip and his mother being “in the trunk.”That could strike some as a clue, or the ramblings of a boy who was then just 2.For authorities in Utah, none of it was enough to bring charges.The man identified by investigators as a “person of interest” — Josh Powell — had already moved from Utah to Washington state, taking with him their two young sons. On Sunday, he torched his house, killing himself and the boys.On Tuesday, investigators said Josh Powell withdrew $7,000 in cash from a bank the day before the deadly blaze. Police from Utah and Washington also searched a storage unit tied to Josh Powell in Pierce County, Wash.Meanwhile a Washington state search warrant obtained by The Associated Press through a public records request showed that police were investigating three felonies in Utah since at least last summer: first-degree murder, kidnapping and obstructing a public servant.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 AP that the case remains a missing persons probe for now.Gill wouldn’t discuss the evidence but said authorities had lacked enough information to file charges.”I think when I talk about it as a missing persons case, that’s because we haven’t located the body of Susan Powell,” Gill said. “Do we think that she may have met harm? Sure. I think that’s been an ongoing assumption with law enforcement.”Josh Powell claimed that on the night Susan Powell vanished, he took sons Charlie and Braden from their home in West Valley City, Utah, on a late-night camping trip. Authorities eventually searched the central Utah desert but found nothing.Susan Powell’s father said that when police went to the family home after she was reported missing, they found a wet spot in the house being dried by two fans. Police have not commented further on what they found.