PARIS (AP) — A cold case in France is heating up, with three new arrests this week over the 1984 killing of a 4-year-old boy named Gregory.

The investigation has involved family rivalries, judicial bungling and 12,000 pieces of evidence — including about 2,000 anonymous letters — in the three decades since his corpse was pulled from a freezing river in eastern France.

The Burgundy gendarme service and Dijon appeals court said in a statement that three people were arrested Wednesday. Local newspaper L'Est Republicain reported that they were a great-uncle, great-aunt and aunt of Gregory's and that they are suspected of complicity in the killing.

A relative was initially jailed but released — and then killed by Gregory's father. Then Gregory's mother was accused of killing her son, before being cleared.