A family member told police about the three babies
The bodies of three babies have been found in a basement freezer in the town of Wenden, in western Germany, prosecutors say.
A woman believed to be the mother of the three has been arrested, a state prosecutor's office spokesman said.
The three were not stillborn, police said, but the cause of death and the infants' ages have not been released.
There have been several similar cases in Germany recently, including a woman jailed for killing her eight children.
The babies appeared to have died shortly after birth and were in the freezer wrapped in plastic bags, the prosecutor's office said.
Post-mortems are to be conducted to establish the cause of death, it added.
One of the bags contained a newspaper from 1988, indicating the babies may have died that year, AFP news agency quoted police investigator Herbert Fingerhut as saying.
Officials said a couple with three children aged 18 to 24 lived at the house.
Two of the couple's adult children found the babies when they were looking for something to eat while their parents were out, police said.
"They both decided to get a pizza and realised that the freezer had to be cleaned up because it was full of out-of-date food," Mr Fingerhut said.
"It was then that they discovered the first bag."
One of the couple's sons went with his parents to the police, who then searched the house and arrested the 44-year-old woman, who is believed to also be the mother of the three babies, German media have reported.
It is not the first such case in Germany.
Two years ago, the body of a dead toddler was found in the fridge of his drug-addicted parents in the northern city of Bremen.
Also in 2006, a woman in eastern Germany was sentenced to 15 years in prison for killing eight of her babies.
She had buried them in flower pots and a fish tank in the garden of her parents' home near the Polish border.