People who take illegal drugs are "supporting the horrific events we saw in Waterford", Irish justice minister Jim O'Callaghan has said.
Kim and Philip English and their sons, Callum and Jayden, died after a suspected arson attack on their home in the Birchwood estate on Tuesday.
On Thursday, police arrested a man in his 20s and a woman in her 30s over the incident.
Gardai said the duo were arrested on suspicion of facilitating a criminal organisation.
Police believe the fire was started deliberately and have launched a murder investigation.
Mr O'Callaghan said: "It was a very significant event, the Gardai are making very significant progress in respect of the investigation.
"What is fuelling this is drugs, it has to be a watershed moment not just for An Garda Siochana or government or politicians, it has to be for the public as well.
"People who are this weekend taking cocaine need to recognise that they are funding organised crime."
He said that by "taking drugs, by funding the drugs industry", people are "supporting the horrific events we saw in Waterford".
Mr English's son claimed earlier this week that his family were murdered because of someone else's €20,000 (£16,800) drug debt.
John James English told RTE, Ireland's national broadcaster, that the family had been targeted for some time but were not involved in drugs and were "innocent".
Garda commissioner Justin Kelly has said he anticipates further arrests over the suspected murders.
Mr Kelly said: "My condolences go out to the English family, in fact the wider community of Waterford, an absolutely horrendous crime.
"We have a full homicide investigation under way, we have made significant progress in the last number of days.
"We significantly made seven searches, we have seized a number of items in connection with the investigation.
"We do anticipate further arrests in this case."
He added that the force has "given every resource" to investigating the deaths.
A post-mortem examination on Mr and Mrs English and the children has been completed but the results are not being released for "operational reasons".
Two other children injured in the attack are still in a critical condition.
Gardai have repeated their appeal for information on the suspected attack, which took place on Birch Avenue.
Mr Kelly said steps are in place to protect those impacted by drugs-related intimidation.
He said it was "part of the drugs business everywhere, in every country".
He added: "We have had a number of prosecutions in this area where we have prosecuted people for drugs-related intimidation.
"What we have certainly seen is an increased use of devices, incendiary devices, petrol bombs. Obviously we are very concerned around it.
"What we are doing is increasing our targeting, not just on the higher-level drugs organised crime groups but some of the medium ones as well."
He said the force had experienced good co-operation from the public in the Waterford investigation.
On Thursday, Sinn Fein TD David Cullinane said the suspected attack showed "utter contempt for human life".
Minister for defence Helen McEntee said the attack was "violent criminality" and that drug debt collection was an "absolute scourge" on society.
"For those who do not feel that they can go to the Garda, I think this is part of some of the problem for people," she said.
Multiple properties have been searched with a number of electronic devices and vehicles seized as part of an "intense" Garda investigation.
Hundreds attended a vigil on Wednesday in the Birchwood area. A joint funeral mass for the four family members will take place on Monday afternoon.
(c) Sky News 2026: Drugs fuelling 'horrific' events seen in Waterford, says Irish justice minister

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