Father Andrew Wagstaff, 69, had spent the evening with his fellow cleric at a rectory near Antwerp, and after taking ecstasy and 'poppers' together and having sex, he suddenly felt unwell, prosecutors said.
The Church of England priest, ordained 30 years ago, was the much-loved chaplain of St Boniface Church, Antwerp, until retiring earlier this year to live near Ilkley, West Yorks.
The circumstances of his death have cast a shadow over his life in the church, particularly as Fr Wagstaff's return to Belgium was timed to coincide with the visit of the Pope there last weekend.
Father Wagstaff and his friend, identified only as 'Pastor B', spent the evening at a rectory in Kalmthout, north of Antwerp, on Thursday, and he died in the early hours of Friday.
In a statement, the Church of England's Diocese in Europe told MailOnline: 'We have been informed of the death of The Reverend Andrew Wagstaff in the area of Antwerp on Friday 27 September 2024.
'Fr. Wagstaff retired as Chaplain at St. Boniface, Antwerp on 30 April 2023 after 17 years and had been living in the UK for the past year.
'Our prayers are with his friends, family and members of his former congregation.'
On Facebook, a US-based organist Jimmy Culp, posted: 'I learned late last night of the death of my friend Fr Andrew Wagstaff in England. I solicit your prayers for the Repose of his Soul.'
The alarm was raised shortly after midnight on Friday when Fr Wagstaff's friend, identified only as Pastor B, called the emergency services, who could not resuscitate his companion.
The sudden arrest of the pastor, visiting colleagues as the Pope travelled through Belgium, left the small parish of Heide in shock, according to local media.
'It appears that the two men had used ecstasy and poppers together and had had sex,' the prosecutor's office revealed on Saturday.
'Two ecstasy pills were also found,' they said..
Poppers refers to amyl nitrite, a liquid compound that can be inhaled for a brief rush of mild euphoria and dizziness.
'Traces of narcotics were found on the victim's body,' Kristof Aerts of the Antwerp public prosecutor's office said.
An initial urine test showed ecstasy had been taken, but an autopsy will be required to prove cause of death.
An investigation was ongoing and the initial autopsy could not immediately provide any conclusive information into the exact cause of the death, the office added.
The 60-year-old priest was questioned by the investigating judge on Friday and gave a statement.
The public prosecutor revealed only that 'some elements of his statement require further investigation'.
He was later placed under arrest, and is now facing charges of 'trafficking in narcotics resulting in death'.
Father Wagstaff had reportedly been visiting colleagues to coincide with the Pope's four-day visit to Belgium late last week.
In 2010, the Rev Wagstaff was appointed chaplain of St Boniface in Antwerp, working under Archdeacon John de Wit, based in the Netherlands.
His duties as Area Dean included chairing the Anglican Council for Belgium, roughly equivalent to a Deanery Synod.
Pope Francis concluded his weekend trip to Belgium on Sunday after facing some of the strongest criticism yet levied during a foreign visit.
In a meeting with Belgian dignitaries on Friday, both King Philippe and Prime Minister Alexander De Croo called for more concrete action to help survivors of abuse by Catholic clergy.
And in later events at two Catholic universities, officials denounced his stance on the role of women in the church and society.
Francis did not specifically mention the criticisms at his last event in Belgium on Sunday, a celebration of Mass at Brussels' King Baudouin soccer stadium.
But the pope did add to the prepared text for his sermon and made a strong condemnation of Catholic clergy abuse.
'There is no place for abuse,' the pontiff said, drawing scattered applause from the estimated 37,000 attendees.
'There is no place for the cover-up of abuse. I ask everyone, do not cover up abuse. I ask bishops, do not cover up abuse'.
The Pope also faced scrutiny on Saturday as he addressed an audience at UCLouvain.
Professors and students issued a press release moments after he finished speaking, saying they wanted to express their 'disapproval' of his views.
The pope's speech at the university largely called for global action on climate change, but he also responded to a letter to him from students and professors that had asked about the Catholic Church's teaching on women.
Francis emphasised that the church, which bans ordination of women to the priesthood, was not run like a corporation. He described women as having 'a fertile welcome, care (and) vital devotion'.