ALLENSTOWN – Authorities are hoping for new leads in their investigation of an Allenstown man's death, and his family is looking for some answers.

The body of Jason Upton, 34, of 98 Main St. was found floating in the Merrimack River on Aug. 2. The Attorney General's Office says a cause of death was never determined, but Upton's family suspects criminal wrongdoing.

Upton's sister, Tracey Sheehan, 42, of Barrington, has established a $1,000 cash reward through the Concord Crimeline for anyone with information that would close the case.

"We fully believe there was foul play," Sheehan said.

Assistant Attorney General Will Delker said the cause of death has been deemed "undetermined."

"We don't know how he ended up in the river," Delker said. "I can't say foul play was involved or was not involved. It's something we're exploring."

Delker said he could not comment on specifics of the case, including whether any trauma was found on Upton's body, because it could jeopardize the investigation.

Sheehan said her brother was diagnosed with bipolar disorder at age 20 and had a substance abuse problem when he died. However, she said many factors in the case point to homicide as opposed to an accident or suicide.

"He was found on the Ferry Street side" of the river, Sheehan said. "There's a spot by the cornfield where they'd build campfires. They like to party over there."

Sheehan said her brother and his friends often used alcohol and drugs at the spot where he was found.

"I think it was a fight that went overboard," Sheehan said. "Because of his bipolar condition, he had no fear and wouldn't back down from anybody. You get people together drinking . . . and they got no sense of a conscience. They lose it."

Upton wasn't typically violent, according to Sheehan, but had shown occasional angry outbursts when he and his wife, Danielle, had lived with her for about a year before moving to Allenstown.

Sheehan said she's received little information about the case from the Attorney General's Office, but has carefully dissected the information that has been given to her.

"The medical examiner keeps saying it's undetermined, but we have to read between the lines," she said. "If there was water in his lungs, they would have said he died of an accidental drowning."

Sheehan said the last person to see Upton alive was their mother, Diane Vattes, 62, at her Manchester home July 25. Upton's wife asked police to conduct a well-being check on July 27.

Sheehan said she has not spoken to Upton's wife since his funeral.

Upton, who loved playing the guitar and became a roadie for a local rock band in the months before his death, would have turned 35 years old Nov. 6. Sheehan and her mother celebrated by visiting his gravestone.

"She goes to the cemetery just about every day," Sheehan said. "We met there on his birthday, Nov. 6, then went back to the house and had cake. It's what she needed to do for herself."

Sheehan said her mother had taken out a life insurance policy on Upton, who often drifted between jobs, but the policy would not pay for funeral expenses because a cause of death hasn't been ruled.

Delker said the investigation continues into Upton's death.

"If there are any witnesses that have information, please contact state police," he said.

Anyone with information can contact the Concord Crimeline at 226-3100 or New Hampshire State Police at 271-3636.