LONGMONT, Colo -- A Longmont man accused of keeping explosive chemicals and handguns in his home was charged Friday with 10 counts of possessing illegal explosives and one count of drug possession.

Ronald Swerlein, 50, a retired electrical engineer, was arrested June 17 after local and federal agencies spent the weekend searching his home. Neighbors had reported hearing three explosions at the house three days earlier.

According to an arrest affidavit obtained by 7News, Swerlein called those explosions in his garage "tiny, tiny tests" he was doing to teach himself about rocket fuel technology. The affidavit says Swerlein told investigators that he "believed the experiments in his house were the safest thing because they were enclosed in his garage. He always made the samples small and covered them with tires."

Authorities said they found more than 400 chemicals in Swerlein's house, including homemade nitroglycerin and MEKP, a volatile chemical that had been stabilized and hidden in the basement.

Officers said they also found model rockets, rocket kits and engines, a launching pad for model rockets, books on homemade explosives, expensive chemistry glassware, a handwritten "to-do" list and warning note, flare guns, a Taser weapon and three metal grenade shells.

They also reported finding magazines from the Animal Liberation Front, which the FBI considers to be a terrorist group.

He and his lawyer, Jeffrey Larson, declined to comment when they walked into a Boulder County courtroom Friday.

Larson has said he believes Swerlein's neighborhood is safe.

But some neighbors are concerned about their community, and are now planning to launch a neighborhood watch program in the area.

"I think it's good to keep an eye on the neighborhood, alert each other if anything suspicious is going on," said Shane Crawford, who lives just down the road from Swerlein. "But as far as what people have in their garage, you'll never know."