Dutch contestant Joost Klein was excluded from just hours before the event following an incident unlinked to the controversy over Israel's participation amid the Gaza war.
"Swedish police have investigated a complaint made by a female member of the production crew after an incident following his performance in Thursday night's Semi Final," the European Broadcasting Union said in a statement.
"While the legal process takes its course, it would not be appropriate for him to continue in the Contest."
Swedish police told news agency Agence France-Presse (AFP) they had questioned a man for alleged "intimidation".
"The offence was committed in the Malmö arena on Thursday evening," police spokesman Pelle Vamstad said.
Dutch public broadcaster Avrotros said in a statement that it found the move "disproportionate", adding that it it was "shocked by the decision".
At the press conference after the second semi-final, Klein repeatedly covered his face with a Dutch flag, seemingly signifying he didn't agree with being placed next to the Israeli contestant Eden Golan.
A representative for Klein did not immediately respond to a request for comment.
Reactions to Joost Klein's expulsion
The 68th version of the contest, normally a festival of catchy songs and tongue-in-cheek kitsch, is taking place amid protests in host city Malmö over the participation of Israel, due to its war in Gaza.
Eurovision expert Paul Jordan told Reuters it was unprecedented for an artist to be expelled on the eve of the final.
"Obviously we don't know what's happened now. He could be found innocent," Jordan said.
"I just think it's a great shame, but the show must go on, as they say."
The incident has nothing to do with the Israeli delegation, Avrotros Eurovision commentator Cornald Maas said.
"It is, among other things, hellish for Joost Klein, who is a unifier, and his team," Maas wrote on social media platform X.
The EBU said in a later statement that Dutch viewers would still be allowed to vote for other contestants and that the Dutch jury result would still be included in the final.
Bookmakers have Croatia's Baby Lasagna, real name Marko Purišić, 28, with Rim Tim Tagi Dim, as front-runner to win the contest, followed by Israeli solo artist Eden Golan, 20, with her song Hurricane.
Other nations high on betting list include France, Italy, Ukraine and Ireland. Streaming data from Spotify also suggests a chance for host nation Sweden.
After Klein's disqualification, 25 countries will compete in Saturday evening's grand final.
Gaza protests at Eurovision
Billed as a feel-good celebration of European diversity, this year's contest has been thrust into the political spotlight with protesters — online and — calling for Israel to be excluded from the competition.
Eurovision organisers have resisted such calls, but demanded that Israel tweak the lyrics of its original entry to remove what they said were references to Palestinian group , which sparked its war on Gaza.
Some booing was heard from the crowd before, during and after Golan's performance in the semi-finals on Thursday, but there was also applause and Israeli flags being waved, according to a Reuters journalist in the auditorium.
In central Malmö, more than 10,000 pro-Palestinian campaigners, including climate activist Greta Thunberg, staged a non-violent protest ahead of the semi-final, waiving Palestinian flags and shouting "boycott Israel".
A smaller group of pro-Israeli supporters, including members of Malmö's Jewish community, also staged a peaceful demonstration in the city, defending Golan and her right to take part in the contest.
Protesters have complained of double standards as the EBU banned Russia from Eurovision in 2022 following its invasion of Ukraine.
