Germany is now seeking the extradition of the Israeli intelligence agent, who was said to have been arrested in Warsaw in early June.
"He was arrested in Warsaw and is suspected of being involved in illegally obtaining a [German] passport," a spokesman for German federal prosecution said on Saturday, confirming a report by German magazine Der Spiegel.
"It's now up to the Poles to decide if they are going to hand him over to Germany."
According to an article to be published on Monday in Der Spiegel, the suspect, identified as Uri Brodsky, was arrested on arrival at Warsaw's airport on suspicions that he helped a member of the hit squad get a German passport in June 2009.
Mahmud al-Mabhouh, a founder of the military wing of the Palestinian group Hamas, was found dead in his hotel room near Dubai airport on January 20.
Dubai is the commercial hub of the federation of seven Arab emirates called the UAE.
Dubai police have released extensive surveillance camera footage they say shows the team of suspects from the hit squad they have linked to the Mossad. Al-Mabhouh had been drugged and then suffocated, Dubai police said.
Twelve British, six Irish, four French, one German and three Australian passports were used by 26 people believed linked to the murder, according to Dubai police.
In many cases, the documents appeared either to have been faked or obtained illegally.
The issue caused a diplomatic row in which the five countries whose passports were used, called in Israeli envoys for explanations.
Source: Al Jazeera