(CNN) -- Authorities have found a second homemade explosive and more of a type of explosive previously discovered in a house in an unincorporated area near Escondido, California, officials said Thursday.
The house occupied by George Djura Jakubec, a computer software consultant who is now under arrest, has been described by authorities as a bomb-making factory. They say it holds the largest cache of the two homemade explosives ever discovered in one spot in the United States.
San Diego County authorities confirmed Thursday they have found pentaerythritol tetranitrate, or PETN, a favorite of al Qaeda bomb-makers that is now the target of new U.S. airport body scans and pat downs.
They also found more hexamethylene triperoxide diamine, or HMTD, in a bottle inside the house, but the two types of homemade explosives were not immediately removed because they are too volatile and the house is too cluttered to negotiate safely, Assistant Sheriff Ed Prendergast said.
Authorities had already recovered 8 or 9 pounds of HMTD, an explosive powder that suicide bombers use, authorities said.
The search of the house also turned up items "suggestive of armed robberies," Prendergast said in a written statement.
In addition to bomb-making charges, Jakubec, 54, is charged with two bank robberies. Now being held in lieu of $5 million bail, he was on probation for a 2009 burglary conviction when he was arrested last week.
Authorities are investigating Jakubec's intentions. He is a Serbian national who is a naturalized U.S. citizen, and he lived in the house with his wife.
Authorities also found Wednesday more blasting caps, adding to others discovered in the past week, but they were not removed from the house, officials said.
A San Diego County hazardous materials team removed chemicals from a shed on the property, authorities said. They included about 4 liters of hydrochloric acid, 1 liter of nitric acid, 25 gallons of sulfuric acid and 50 pounds of hexamine.
A bomb squad from San Diego County agencies and the FBI has suspended a search inside the home until Wednesday, as authorities study how to proceed within the cramped, cluttered home without causing a blast, Prendergast said. Authorities also found inside the house some more hazardous chemicals, which also won't be moved for now, he said.
The sheriff's department has secured a perimeter around the suburban house and closed the street off except to residents, Prendergast said.
One explosives expert described the eight or nine pounds of previously discovered HMTD as potentially "devastating."
"If you had 8 or 9 pounds in a vehicle in a street, you have a pretty large and devastating car bomb," said James Cavanaugh, a retired special agent of the federal Bureau of Alcohol, Tobacco, Firearms and Explosives.
"Inside a home, it's going to blow all the windows and doors and walls out, but it's not going to destroy the neighborhood. People would be in danger if they were immediately in front of the house or adjacent to the house," he said. " It would be almost like a gas explosion."
Bomb squads must be wary of potential booby traps, Cavanaugh said.
"These explosives, like HMTD, I call the devil's own mixtures, and they can be set off by shock, friction, static electricity, heat, flame or even a chemical reaction," he said. "Added to the danger is that they are difficult to find in a filthy hoarder's hovel."
Outside court this week, Jakubec's wife, Marina Ivanova, was distraught.
"He's crazy," she told camera crews. "I think he lost his mind. He lost his mind or something. ... I know that he was collecting, obsessively collecting stuff."
Bomb technicians must work slowly inside the house because the slightest friction -- such as opening a drawer -- could ignite the explosives, Prendergast said.
Jakubec appears to be a hoarder, and the clutter of paper and boxes in the house makes the hunt for explosives more difficult, the assistant sheriff said. Bomb crews were wearing less gear so they can move about the house without brushing up against anything and accidentally triggering the explosives, he said.
"We are wearing some protective gear, not the big protective gear" that resembles moon suits, Prendergast said. "It's just not practical for this operation."
Authorities discovered the explosives last Thursday after a gardener was injured when he unwittingly set off some of the HMTD powder in the back yard, Prendergast said. The blast went up one side of his body, from lower leg to head, he said.
"We believe he scraped against some of the powder in the yard, and the friction caused it to explode," Prendergast said. "Apparently the suspect was experimenting in his yard, and some of it got left over" the ground, he added.
The 8 or 9 pounds of HMTD was in six jars that had apparently been moved out of the house and into the back yard, he said.
Last Friday, authorities had to evacuate two nearby houses and even closed down the southbound lanes of nearby Interstate 15 for three hours, he said. The two adjacent houses remained evacuated Wednesday, he said.
"It's amazing he didn't blow himself up. He must have some knowledge of how to do this safely," Prendergast said.
"Part of the story should be about the bravery of the bomb technicians and haz-mat team, for risking their lives trying to build a case against this guy so that justice can be served, and trying to render the site safe so that homeowners can return to their homes," he added.
During Wednesday's search, only two or three bomb technicians entered the house for less than an hour and seized a computer and other items, Prendergast said. The crew videotaped the interior and will review the tape later to determine their next mission, officials said.
In recent days, technicians found improvised grenades that weren't live, he said.
"If you look at the video of this, you can see items piled on top of items. It gives you a mental picture of how difficult it is," Prendergast said. "Counter space and tables, every bit of space had items piled on top of items -- papers and boxes.
"We only pull things out that have easy access," he added.
Law officers have defined "a hot zone" consisting of the house itself and the two nearby evacuated houses. A "warm zone" is the street in front of the house, and a "cold zone" is the area beyond a police tape where the media and public are allowed to stand, Prendergast said. At night, after bomb crews have finished their work, the hot zone is reduced to just the house, he said.
Authorities said the HMTD discovered inside the house Wednesday is stored in a bottle.
"We have not removed it yet. It's too dangerous to move. Any movement can set it off," Prendergast said.
"We have a saying: We'll go as fast as we can but slow as we must," he added.