Nearly a month after the explosion in West that killed 15 people and injured dozens, investigators say they're close to finishing their probe and could announce their findings in the next two weeks.
They've already ruled out a natural cause such as lightning, said U.S. Bureau of Alcohol, Tobacco and Firearms and Explosives Agent Francesca Perot.
The remaining possibilities are an accident, a deliberate act or undetermined, she said.
Meanwhile, the court-appointed attorney for volunteer medic Bryce Reed, who has been charged with having a small pipe bomb, said Reed didn't do it.
"Mr. Reed had absolutely nothing to do with the West fertilizer explosion on," said Waco attorney Jonathon Sibley. "There's absolutely no connection between him and that."
Federal prosecutors have said they will not speculate -- and won't name Reed as a suspect in the explosion or clear him of wrongdoing.
The Texas Rangers launched a criminal investigation into the explosion just hours after Reed's arrest early Friday morning.
Sibley said Reed will plead not guilty to the charge of possessing explosives at a detention hearing on Wednesday afternoon.
"What we're saying is, he disputes the allegations that we know about, that they've accused him of, and we're looking forward to pleading not guilty and going to court on this," he said.