SALEM, Ind. (AP) _ They were in the same Cub Scout pack and competed for for leading roles in high school plays.

But no one suspected the rivalry between Frank Newkirk Jr. and John M. Hubbard III had any connection with 13 bombs planted around town last summer.

Hubbard, a 31-year-old factory worker, and a co-worker at Ferraloy Industries, 42-year-old Gerald Conrad, were indicted Thursday in Indianapolis, accused of planting explosives targeted at Newkirk, a state lawmaker and mayor's son.

They were arrested Wednesday on charges of possession of stolen dynamite, conspiracy, making bombs and attempting to destroy roads and buildings in this community of 6,000. Three of the bombs fizzled; none of the 13 exploded.

Jim Brown, manager of the Ferraloy plant where the suspects worked, said he was shocked by the arrests. ''We have seen nothing that would cause you to believe something was amiss or that anything like this was going on,'' he said.

Hubbard was a machine operator at the plant, which makes auto and appliance parts, for about two years. Conrad had worked about seven years as a design manufacturer.

Authorities have declined to speculate on a motive for the bombs, but a crimnal complaint filed in federal court described Hubbard is a ''lifelong rival'' of Newkirk's.

''If there was a rivlary, it was in John's mind,'' Newkirk said Thursday. ''I understand maybe he wanted to achieve some of the things I had.''

Newkirk, a Democrat, said the two men didn't see eye to eye on politics.

''John believed government was too involved in peoples' lives,'' Newkirk said. ''He had said things in the past that sounded like he was an anarchist. If the bombs had gone off, it would not have caused a government to fall, but it would have created a lot of havoc.''

The rivalry can be traced to their Scout pack, which was led by Newkirk's father, Mayor Frank Newkirk Sr.

''My father really liked John. John was overweight and I was overweight, too,'' the younger Newkirk said. ''My father realized how cruel children can be about things like that, and I think my father kind of went out of his way to look after John.''

Newkirk said Hubbard once complained about losing out to Newkirk in competing for roles in high school plays. ''He did express some frustration to me back in high school that there was no use for him to try out,'' Newkirk said.

Newkirk, a former deputy prosecutor elected to the Legislature in 1984, became suspicious of Hubbard about two weeks after the bombs were found. He and his wife, Denise, were working in a booth at a county fair when they ran into Hubbard.

''After a while, he began to talk about the bombings,'' Newkirk said. ''He had a lot of information. He told me where the bombs were located, what the dynamite would do if it were exposed to fire and what would have happened if the bombs had gone off.''

Newkirk took that information to police.

Hubbard's mother, Opal Kramer, said she was not surprised her son was knowledgeable about the bombings. ''Everybody in town was talking about the bombings,'' she said. ''The pictures were very vivid on TV and in the papers.''

She described her son as a vocal, opinionated, intelligent man who liked guns but would not harm anyone ''unless he's under the influence, and I don't know that he would (harm anyone) then.'' She said her son had been hospitalized for about a month for treatment of alcohol abuse earlier this year.

Mrs. Kramer said she believes her son was arrested because authorities ''were under some pressure to arrest somebody because it's been so long.''

''They have coincidental evidence that may or may not be true,'' she said, adding she he is innocent.

Newkirk said he is relieved that Hubbard and Conrad were arrested.

The bombs were planted around town, under bridges and behind buildings. The largest was placed outside Newkirk's law office.

The morning he found the 52 sticks of dynamite under a stairwell behind his office is vivid in his memory still. Although no bombs were found at the couple's home two miles from the office, the incident has changed their lifestyle.

For at least a month afterward, the Newkirks would not allow their children to go out in the yard unless one of the parents was present, Mrs. Newkirk said.

''Every night I still walk around the house with a flashlight to make sure there's nothing out there,'' Newkirk said. ''That's probably a habit I'll never end.''

Hubbard and Conrad were being held without bail Thursday in Marion County jail in Indianapolis. A federal grand jury indicted the two on 29 felony counts, including conspiring to manufacture destructive devices, the manufacture of 14 bombs and attempting to damage buildings and bridges.