Ukip MEP Mike Hookem is understood to be the politician who was involved in an "altercation" with Ukip leadership favourite Steven Woolfe.
Mr Woolfe was rushed to hospital with a suspected brain injury after collapsing in European Parliament earlier.
He has since tweeted he is "sitting up" and is feeling "brighter and happier" but is being kept in hospital overnight for further tests.
Ukip MEP Steven Woolfe has said he is "feeling brighter" after being rushed to hospital with a suspected brain injury.
Mr Woolfe was taken to a Strasbourg hospital on Thursday following reports he was involved in an "altercation" with another party MEP.
Nigel Farage had said that the 49-year-old, a contender for the Ukip leadership, was in a "serious" condition.
But Mr Woolfe later released a statement from hospital, saying: "The CT scan has shown that there is no blood clot in the brain.
"At the moment I am feeling brighter, happier, and smiling as ever."
He said he is being kept in hospital overnight "awaiting secondary tests to make sure everything is fine".
I would like everyone to know that the parliamentary staff, the UKIP MEPs with me and hospital staff have been brilliant. Their care has been exceptional. I am sitting up, and said to be looking well. The only consequence at the moment is a bit of numbness on the left hand side of my face.
MPs have sent their well wishes to Ukip's Steven Woolfe after he was taken to hospital in the aftermath of an "altercation".
Mr Woolfe was taken to a Strasbourg hospital on Thursday and said to be in a "serious" condition.
MPs from across UK political spectrum have taken to Twitter to extend their best wishes.
My thoughts are with @steven_woolfe and his wife and daughter at this anxious time and I wish Steven a speedy and full recovery.
Ukip MEP Steven Woolfe is "getting better", according to a party spokesman.
Mr Woolfe was taken to hospital in Strasbourg in a "serious" condition following reports of an "altercation" between party MEPs.
Ukip leadership contender Raheem Kassem had tweeted that the 49-year-old was in a "life-threatening" condition.
"It looks like he is getting better," the spokesman said when asked about Mr Woolfe's condition.
Ukip's Steven Woolfe is in a "life-threatening" condition following an altercation with fellow party MEPs in Strasbourg.
Mr Woolfe, who turned 49 today, was taken ill after walking out on a vote at the European Parliament.
Woolfe, who declared on Wednesday his intention to run as party leader, was reported by Nigel Farage to be in a "serious" condition upon being taken to hospital.
Fellow leadership contender Raheem Kassem tweeted that he believed Woolfe was in a "life-threatening" condition.
I've just heard Steven Woolfe's condition is life threatening. Please keep him in your thoughts and prayers.
Ukip's Steven Woolfe said he is "brighter and smiling as ever" after he collapsed following an "altercation" in Strasbourg.Read the full story ›
Steven Woolfe has become the first leadership contender to throw his hat in the ring following the shock resignation of Diane James.
Mr Woolfe was barred from standing in the last leadership contest after submitting his nomination papers 17 minutes late.
His announcement came as Nigel Farage confirmed he would be carrying on as interim leader until a permanent successor was in place - prompting a furious row within the party.
Nigel Farage has said he thinks Diane James' decision to quit as leader of Ukip could have been because of an attack she experienced at Waterloo Station.
Shortly after winning the leadership contest, Ms James was spat on and verbally abused on a train platform. Mr Farage said the incident could have caused "a realisation that she'd taken on a job that was going to be 24/7 that was going to involve her having security with her the whole time, I mean you take this job, your life is no longer your own".
The acting Ukip leader added that he would much rather Ms James recognised that the job was not for her now rather than months after accepting the position saying it "isn't where we need to be but it's not the end of the world."
Nigel Farage will continue as "acting Ukip leader" until a new leader is elected following the resignation of Diane James after just 18 days.
But he ruled out standing as leader himself, telling Adam Boulton on Sky News: "I've done my bit, I'm still very much a member of the party.
"But it is it is time for someone else to do the job."
He said he was sorry that James resigned, adding that he thought she had "all the qualities for the job".
It's a pretty rotten job being leader of any political party and I think being leader of Ukip is probably more rotten than all the others.