A woman who was arrested on suspicion of murder as part of the investigation into the death of a baby boy in Ireland almost 40 years ago has been released without charge.

A man in his 60s who was also arrested remains under detention at a Garda station in the south of the country.

The body of the five-day-old infant, known as Baby John, was found with multiple stab wounds in a bag on a beach in Co Kerry in April 1984.

The man and woman were arrested in the Munster region on Thursday “in relation to the discovery of the body of a male infant at White Strand, Caherciveen, County Kerry”, according to a garda statement.

The high-profile discovery became known as the “Kerry Babies” case, and would lead to a state apology over the treatment of a local woman.

Joanne Hayes was arrested and charged after Baby John’s body was found in 1984, but the charge was later dropped and a tribunal of inquiry was set up to probe the handling of her case by Gardai.

Advances in DNA profiling then confirmed that Ms Hayes, as she always maintained, was not Baby John’s mother.

In 2018, Taoiseach Leo Varadkar, justice minister Charlie Flanagan and An Garda Siochana apologised to Ms Hayes.

In January 2018, An Garda Siochana announced a review into the death of Baby John, and since then its Kerry Division has carried out an “extensive” investigation, supported by the Garda Serious Crime Review Team.

Hundreds of people have been interviewed and more than 560 lines of inquiry have been initiated.

In September 2018, Baby John’s remains were exhumed and taken to the morgue at University Hospital Kerry in Tralee for examination, and were reinterred later that afternoon.

Baby John is buried at Holy Cross Cemetery in Caherciveen.

“The arrests are a significant development in this investigation in an effort to establish the truth surrounding the death of Baby John in 1984 and deliver justice for Baby John,” said lead investigator Superintendent Flor Murphy.

“I am again appealing to the public for any information in relation to the death of Baby John in 1984.

“Anyone who comes forward will be treated with sensitivity and compassion.”

Anyone with information is asked to contact Killarney Garda Station on 064 667 1160, the Garda Confidential Line on 1800 666 111 or any Garda station.