The parents of a Missouri teen rescued from an alleged kidnapper told talk show host Oprah Winfrey in an interview aired on Thursday they believe he was sexually abused during the more than four years he was missing.

"OK, I'm going to go there and ask you, what do you think happened? Do you think he was sexually abused?" Winfrey asked Craig and Pam Akers, parents of 15-year-old Shawn Hornbeck.

Both nodded and said, "Yes."

The interview, which aired on CTV, was broadcast on the same day that the man accused of kidnapping Shawn pleaded not guilty to charges of kidnapping another boy, 13-year-old Ben Ownby.

Pizzeria worker Michael Devlin, 41, pleaded not guilty to kidnapping a child under age 14 via video link from the county jail. Security concerns have kept him from appearing in person at the courthouse.

Shawn and Ben were found last week in Devlin's apartment in Kirkwood, a St. Louis suburb. Shawn had been missing for more than four years, Ben for four days.

Devlin's attorney, Michael Kielty, declined comment on the sexual abuse claim, saying he hasn't seen evidence.

"The only thing I have is an allegation," he said.

Authorities have said that Devlin confessed to kidnapping Ownby, but Kielty would not discuss those claims.

'I prayed,' boy tells Oprah

Most major media organizations make it a policy not to identify alleged victims of sexual abuse, while journalists are prevented from naming them in Canada. But this case has received widespread publicity.

When Winfrey asked if Shawn son had been tortured, the boy's stepfather said that something had obviously happened to dramatically change the boy.

"I have no doubt that mentally he's not the same boy he was," Craig Akers said.

Shawn told Winfrey he had never given up hope of being reunited with his family.

"I prayed that one day my parents would find me and I'd be united," he said.

Shawn said he was not ready to divulge details of his alleged abduction. However, he told Winfrey that he did have some freedom and telephone access.

He even left a message on a website created by his parents, asking how long they were going to look for their son and signing his name "Shawn Devlin."

The boy's stepfather said he saw the posting but dismissed it as a crank message, because "we had been saying all along that we will never stop looking for our son."

Winfrey said the boy told her off-camera that he was "terrified" to contact his parents during the last four years.

The boy's parents told the talk show host they have not asked their son what happened based on advice from therapists, but they are sure that fear kept Shawn from contacting them.

"There has to have been something held over his head," Craig Akers said. "There's no way in the world that if he was able to do whatever he wanted to do ... there's no doubt in my mind he would have (come home)."

Shawn disappeared in October 2002 while riding his bicycle in the St. Louis suburb of Richwoods. He was found at Devlin's home about 64 kilometres away, police said.

Devlin under investigation

The Associated Press has learned that Devlin is also under investigation in the 1991 disappearance of another Missouri boy.

Lincoln County sheriff's deputies told AP he is the "most viable lead" in the case of Charles Arlin Henderson, who was 11 when he disappeared in 1991.

Like Shawn and Ben, the boy lived in a rural town about an hour from St. Louis.

"If you were to take a photo of Arlin Henderson and you place it next to Shawn's picture, there is a striking resemblance," Lincoln County sheriff's Lt. Rick Harrell said.

Authorities reportedly began to investigate the 1991 case after Devlin was arrested.

Det. Chris Bartlett said a witness reported seeing a man taking photos of the boy, who went by the name of Arlin, before he vanished.

FBI spokesman Pete Krusing would not confirm, however, whether the agency was probing a connection between Devlin and the 1991 case.

With files from The Associated Press