A homeowner was arrested early Sunday morning after more than 200 chemical compounds and liquids were found in his home, several of which could have caused significant damage if detonated, Longmont police officials said.Ronald Swerlein, 50, was arrested around 4 a.m. near his home as he tried to get back into his residence. Police said they found Swerlein returning to the crime scene with a screwdriver and a flashlight.During execution of a search warrant, police said they found many blasting agents and highly flammable fuels and oxidizers in the home that presented significant hazard concerns. Lead azide, nitroglycerine, PETN and thermite were among the agents found in the home.Bomb squads had to detonate the nitroglycerine in the home's driveway Saturday night. No one was injured in the controlled blast.Police did not immediately arrest the couple who lived in the home. However, police said after collecting evidence, they determined Swerlein to be the primary suspect. He was arrested and charged with two felony counts of possession and use of explosives. Each count carries a prison sentence of two to 12 years.Tim Barth lives three doors down from the house and said the couple living there usually kept to themselves. Police said Swerlein is a disabled electrical engineer who once worked for Hewlett Packard. They said he ordered most of his explosive stockpile online."The UPS truck is always parked over there," Barth said. "I mean he was getting UPS shipments like every day of the week."Police said additional charges may be added later in the investigation.Swerlein's home continued to be searched for more evidence throughout Sunday.The incident began on Friday when police arrived at Swerlein's home with a search warrant after reports came in that there were explosions coming from the home over the past year. The incident eventually escalated to a hazardous materials situation requiring the assistance of the Environmental Protection Agency and the 8th Civil Support Team from the Colorado National Guard.Longmont police said they were serving the warrant in the 2400 block of Sunset Drive Friday evening and found what was believed to be an explosive device. SWAT teams and the bomb squad were called out. Some residents in nearby homes were evacuated for a time Friday, but were allowed to return to their homes around 10 p.m.The search resumed Saturday morning and more than 200 different chemicals were found, officials said. The cleanup required specially trained experts to be brought in. The amount of chemicals that have been found and the dangers the chemicals pose made the cleanup process very slow, police said.The situation got more serious Saturday night. While bomb squad members were processing chemicals in the home, they found about a half-pound of nitroglycerin, an extremely volatile chemical that cannot be moved without risk of explosion.Officers evacuated 30 homes and used reverse-911 system to warn people within a 1/2-mile radius of the blast.They detonated the nitroglycerine in the suspect's driveway, and the explosion could be heard and felt throughout the area."Over the last 12 months, we've had reports of explosives in the area and were unable to pinpoint it until recently because of our investigation and tips, citizens calling in," said Longmont police Cmdr. Craig Earhart.