HOULTON – Maine State Police detectives may return to the Amesbury, Mass., home of the sister of a man believed to have been responsible for poisoning 16 people in his church nearly a month ago.

Police visited the residence on Sunday, but weren’t saying Thursday why they were at the home of Norma Bondeson, 61, or what they might have found.

“It’s not the first time we’ve been down there, and it may not be the last,” Stephen McCausland, Maine Department of Public Safety spokesman, said. “It’s not something we’re talking about.”

Police believe that Bondeson’s brother, Daniel Bondeson, was involved in the April 27 incident at the Gustaf Adolph Evangelical Lutheran Church in New Sweden that left one man dead and 15 others hospitalized after they drank arsenic-laced coffee after a worship service.

Five days later, Bondeson shot himself in the chest, leaving a suicide note that led investigators to believe he was involved in the incident, but did not act alone.

The Reverend Hans Arnesen, Associate Bishop of the New England Synod, said the effect of the ongoing investigation on the New Sweden congregation was traumatic. He said continued suspicion of church members “keeps the deep wound open.”

Two victims remain hospitalized at Eastern Maine Medical Center, one in good condition and the other in fair condition, according to an EMMC representative.

Norma Bondeson has lived in the house in Amesbury for more than 10 years, but reportedly had taken an increasingly active role in the New Sweden church.

The house where she lives is for sale. She had spent much time in the winter with her brother in New Sweden.

On Thursday, McCausland would not say if Norma Bondeson was in any way suspected of being connected with the poisoning.

“We have not been naming names, and we’re not starting now,” he said.

He said investigators have amassed a large amount of information from interviews, evidence at Daniel Bondeson’s home and from FBI profilers. He said detectives have worked hundreds of hours on the case.

“We’re convinced [Daniel] Bondeson didn’t act alone,” McCausland said. “We don’t know how many, but we’re going to find out.”

The Associated Press contributed to this report.