A man police say set off an explosion in his car is held without bail after investigators found bomb-making materials inside the vehicle.

Police say they don't suspect terrorism, and there didn't appear to be any risk to others.

Thirty-six-year-old Joseph Brennan Jr. of Norwell pleaded not guilty Monday to possession of an incendiary device. Authorities say he faces more charges after they found explosives at his home.

Brennan was arraigned at a hospital where he's being treated for injuries from the Saturday car explosion in Quincy. His defense attorney didn't comment.

A police report says Brennan told a bystander after the explosion: "I'm an idiot. I lit a cigarette with the gunpowder in the front seat."