HARTFORD, Conn. (AP) – Howard Fish said he felt as if he had been punched in the stomach when he received a call at work from the FBI Friday telling him his son was in custody after authorities found a stick of dynamite in his airline luggage.

“When the FBI calls and says, ‘Do you have a son named Howard Fish?’ you don’t have a great feeling,” Fish, of Old Lyme, said Friday night.

A stick of dynamite was found in the checked luggage of Howard McFarland Fish, 21, on a Continental Airlines flight in Houston. It was one of six security incidents Friday that caused U.S. flights to be diverted, evacuated or searched.

Fish’s flight was traveling from Argentina.

Federal authorities were investigating why Fish, who got off the plane in Houston before it continued to Newark, N.J., had the explosive, FBI spokeswoman Shauna Dunlap said.

Fish was in federal custody and authorities determined his actions were not acts of terrorism, according to the Bureau of Immigration and Customs Enforcement.

The elder Fish said in a telephone interview from his home Friday night that he and his son communicated by phone and e-mail. He characterized his son as a typical college student who “wanted to see all the different places before he’s too old.”

He was traveling alone in South America for more than three weeks and bought the dynamite while on a trip to a silver mine in Chile or Bolivia.

Operators of the mine that he visited directed Fish, a student at Lafayette College in Easton, Pa., to buy presents for the miners. He bought a stick of dynamite and ended up keeping it.

“He threw it in his suitcase,” his father said.

Houston Fire Department Assistant Chief Omero Longoria said Fish told authorities he works in mining and often handles explosives. Longoria said federal officials were investigating whether the explanation was true.

The elder Fish said he is certain his son intended no harm, saying the younger Fish is “absolutely appalled” at violence. Keeping the dynamite was instead careless, the father said of his son.

“What a stupid, stupid thing to do in today’s world,” Fish said.

Fish, who said he is in the communications business, and his wife, Carter, plan to leave for Houston on Saturday to meet with their son and begin handling the legal troubles.

“I am absolutely confident of what happened,” he said. “It’s a 21-year-old kid not paying careful attention to the press and thinking it would be cool to have a piece of dynamite.”