He was repeatedly asked by MPs for evidence of his claim and a Muslim group has made an official complaint.
The 22 March bomb attacks at Brussels airport and Maelbeek metro station left 32 dead and hundreds more wounded.
Separately a new report says one bomber worked at the airport for five years.
Mr Jambon, whose centre-right nationalist New Flemish Alliance is the largest party in parliament, has been broadly criticised for telling a newspaper that a significant section of the Muslim community danced after the attacks,
One political opponent, Katja Gabriels, warned him that a member of the government could not make such generalisations and insult a whole section of the community.
Others called for facts and figures to back up his remarks.
"For days now people are focusing on the word 'significant' and talking about how many instances, how many police reports etc. I'll tell you straight: I don't have police reports. There are some, but not many," Mr Jambon told MPs.
"Everyone knows that these things happened. Do we have to wait for an official police report to confirm the existence of these facts?"
He also reminded his colleagues that stones and bottles were thrown at police after they arrested Paris attacks suspect Salah Abdeslam, four days before the Brussels bombings.
One police officer told Flemish TV that he had witnessed three separate incidents after the Brussels attacks of young people laughing and making a V-for-victory sign with their fingers. But he said he had not seen anyone dancing.
Meanwhile a report citing sources by Flemish broadcaster VTM (in Dutch) said airport suicide bomber Najim Laachraoui had worked for five years for a company that operates at the facility until late 2012, shortly before he travelled to Syria to join so-called Islamic State.
Laachraoui, 24, blew himself up with Ibrahim el-Bakraoui little over an hour before el-Bakraoui's brother, Khalid, attacked the metro with a suicide bombing in the heart of Brussels' European quarter.
The federal prosecutor told the BBC it had no comment on the report "because we don't have this information".
Laachraoui has emerged as the bomb and weapons expert in both the Paris and Brussels attacks. He would have had a security pass and would have known about airport security, VTM said.
The report also spoke of a secret prayer room used by radicalised employees at the airport which was shut down by police shortly before the attacks.
Separately, another of the Paris attacks suspects, Salah Abdeslam, was accused on Thursday of attempting to murder four police officers who were wounded in Brussels a week before the March bombings.
Algerian Islamist Mohamed Belkaid was killed in a shootout when police raided a flat on 15 March, but Salah Abdeslam and another suspect, Amine Choukri, escaped. They were arrested three days later.
Salah Abdeslam is expected to be extradited to France shortly, and the Belgian accusation is not expected to affect his transfer because he has not been placed under an arrest warrant.

The pair made the announcement through what can only be described as a gushy YouTube video.
Set to music during an ultrasound scan, you see the pair with delighted smiles, rubbing noses.
The baby is due in May this year. The couple shared the news in the video after rumours of the pregnancy surfaced on Friday in a gossip column.
"Today the media speculated about some big news in our life. So we decided to share it with you ourselves," the couple said in the video posted Saturday on the YouTube account of Macklemore's musical partner, Ryan Lewis.
Within hours of the video being posted fans of the Grammy-award winner, whose real name is Ben Haggerty, shared tributes and best wishes for the happy couple.
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Belgian Interior Minister Jan Jambon has come under fire for saying that a "significant part of the Muslim community danced" in response to the Brussels bomb attacks.
[NEXT_CONCEPT]
Macklemore and his fiancee Tricia Davis are expecting their first baby together.