A former Pittsburgh police officer is being held in the Allegheny County Jail on federal charges that he possessed at least three explosive devices.

Paul Anthony Palmer Jr., who previously was convicted in a 2003 road-rage incident, is charged with four counts in U.S. District Court and will have a detention hearing Tuesday. He was indicted July 24.

According to two affidavits of probable cause filed in his case and unsealed Thursday, Mr. Palmer was at his mobile home on Redwood Drive in Oakdale on May 1 when there was an explosion.

When officers from North Fayette arrived, they found that windows had been blown out of the trailer, and an awning ripped off. Mr. Palmer, 38, was sitting on a step out front with singed hair, burns to his upper chest and a severely damaged left hand, which later had to be amputated.

A patrol officer who spoke briefly to Mr. Palmer at the scene said "Palmer stated he was on the couch watching the news while his friend was in the kitchen cooking something."

Neither officers nor a maintenance man at the trailer park ever found the friend. The rear door to the trailer was locked from the inside, according to the affidavits.

When officers entered the home, they saw a large amount of blood on the kitchen floor and spattered on the walls.

Two people in the community described hearing a loud, "kaboom" type of explosion, agents from the federal Bureau of Alcohol, Tobacco, Firearms and Explosives wrote in the affidavit.

In conducting a search of the home, investigators found numerous components for improvised explosive devices, including cardboard tubes, black powder, red phosphorous and a green pyrotechnic fuse hidden in the padding of an armchair. They also found two small bombs, advertised to discourage nuisance wildlife. In the kitchen, where they believe the explosion originated, the area was blackened and smelled of burnt gun powder. They also found near the stove and in the sink "blast-affected cardboard tubing."

Mr. Palmer's defense attorney, James Wymard, said he believes his client told investigators he had the devices to blow up pumpkins in the woods.

"I don't think they will find he had any intent on using these to harm any human being," Mr. Wymard said.

But when agents searched Mr. Palmer's home, they said in their affidavits, that they also found a large amount of literature from white supremacy groups, in particular the Aryan Nation. There were 15 books and two flags, they wrote. Mr. Palmer also has a number of tattoos consistent with those groups.

The day after the explosion, Mr. Palmer's wife, from whom he was separated, contacted police and told them her husband had put a backpack in her trunk about a week before. When she turned it over to them, investigators found a small explosive that had flash powder and steel BBs in it.

Mr. Palmer has told police he bought the explosive components over the Internet seven to eight months before the explosion.

Mr. Palmer was previously convicted of aggravated assault for firing at a passing motorist on the Parkway West on Dec. 3, 2003. He was sentenced to time served plus three years' probation.

At the time of the incident, Mr. Palmer, an officer with Pittsburgh for more than 10 years, had been off-duty for a year with carpal tunnel syndrome. He resigned after his arrest.