(CNN) — Bomb technicians in unincorporated Escondido, California, continued working Wednesday inside the house of a man who held “the largest” cache of certain homemade explosives ever found in one place in the United States, authorities said.
Authorities have already recovered 8 or 9 pounds of hexamethylene triperoxide diamine, or HMTD, an explosive powder that suicide bombers have used across the globe, San Diego County Assistant Sheriff Ed Prendergast said.
A gardener was injured when he unknowingly ignited the HMTD powder in the backyard last week, said Steve Walker, a spokesman for the San Diego County district attorney’s office.
Police believe the home also contains pentaerythritol tetranitrate, or PETN, another explosive, which was used in the 2001 shoe bomber plot and during October’s cargo plane bomb attempt, Prendergast said.
The homeowner, George Djura Jakubec, 54, is being held in lieu of $5 million bail and has been charged with 28 felonies: 13 counts of possession of a destructive device, 13 counts of possession of ingredients to make a destructive device and two robbery counts.
The two robbery charges are related to two bank heists, Walker said. Jakubec pleaded not guilty at his arraignment Monday, he said.
Jakubec is a Serbian national who is a naturalized U.S. citizen, and authorities are investigating his background, Prendergast said.