The Nordic Nightmare tested positive for a banned “non-steroid substance” just days before his brutal knockout loss to AJ earlier this month.
Helenius, 39, was drafted in as a short-notice replacement following DillIan Whyte‘s multiple failed drug tests and, like his former opponent, has vowed to clear his name.
The veteran heavyweight said: “I want to say something very clear in my own words right now with absolutely no exception.
“I did not use any performance enhancement now or ever. I have been tested my entire career.
“I was just told that I tested positive for the presence of a non-steroid substance in my system.
“And I wanted to send an immediate direct message to Anthony Joshua and boxing fans that I didn’t cheat and never would.
“I volunteer to work with VADA and the BBBofC to do whatever it takes to clear my name.”
Joshua, 33, continued his career rebuild with a spectacular seventh-round knockout of Swedish-born Finn Helenius at The O2.
A long-overdue grudge match with former WBC heavyweight champion Deontay Wilder is now in the offing for the Watford warrior.
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Negotiations over the Saudi showdown – which is being targeted for January – were at an advanced stage before the Helenius fight and promoter Eddie Hearn hopes to finalise it in the coming weeks.
When asked for a timeline on the fight being a done deal, Hearn told Fight Hub TV: “Two or three weeks.”
The Matchroom Boxing chief added: “I’ve been to Saudi Arabia twice to negotiate this fight. I’ve had two meetings, three meetings in London.
“I’m not doing it for banter. My instructions from Anthony Joshua [are] ‘I want to fight Deontay Wilder.’
“The only way this fight doesn’t happen is if Saudi doesn’t deliver the fight.
“[Wilder manager] Shelly Finkel, Wilder, as far as I’m hearing from them directly, they are in. We are in.
“We just need to sign a contract and go through the procedures to get that done.”
Should the negotiations collapse, Hearn insists Joshua will be back in action before the end of the year.
He said: “If it doesn’t happen, I think he’ll (Joshua) fight in December.
“But I’m not spinning that fight. All of our efforts have been for that fight.
“Honestly I wouldn’t waste my time flying all around the world trying to pretend that that’s the fight we want.
“That is the fight we want. It’s a massive fight, massive money, and that is what I have been instructed to deliver for AJ.”