. >> reporter: it was about 3:50 a.m., when kiowana heard the loud boom.till shaking, she took out her phone, recording the inferno. >> lord of our house was going to catch on fire. >> reporter: the home which was under renovation, completely leveled. >> we did see the basement block had bulged out, which would be indication that something happened internally forcing them out. >> reporter: tonight investigators are sifting through debris, hunting for answer. no official cause just yet. but luckily, no one was home at the time. alex perez, abc news, milwaukee. >> that scene is just unbelievable. >> ah. >> it's just almost unrecognizable as having ever been a house. >> it's incredible. we've had many occasion like that over the last couple years. we've seen that scene in new jersey that was caught on camera where several houses sort of exploded because of a gas leak. and then we saw an incident just this past week or so in minneapolis where that academy blew up and ended up killing two people. >> the odd thing in this case is that police don't believe that t