Farmington, Maine — The father of a 4-month-old boy whose death was classified nearly 38 years ago as sudden infant death syndrome was arrested Friday after detectives concluded it was homicide.

Burton "Ben" Hagar, 62, of Farmington, was charged with murder after being indicted this week, said Stephen McCausland, spokesman for the Maine Department of Public Safety.

Hagar is accused of killing his son, Nathan, who was found unresponsive in the family's Brunswick apartment and died at a hospital on May 9, 1979. State police quietly reopened the case in 1991, and the investigation was augmented by the state police cold-case unit, which became fully staffed as of last year.

"This is the first arrest as a result of the work of the unsolved-homicide unit. And there will be others as the work continues," McCausland said.

The body was not exhumed, and authorities aren't saying how they believe the infant died.