(Bloomberg) -- Danish prosecutors who charged hedge-fund manager Sanjay Shah with running a $1.6 billion tax fraud say they’re looking at a “number of other suspects” in the case.

Prosecutors said they’ll be in a position by March to decide whether to press charges against more members of a network that they say was set up to defraud the government in the biggest and most complex tax case in history.

Prosecutors still need to finish some of their investigation, including interviewing “several people,” Per Fiig, acting head of the State Prosecutor’s Office, said in an interview.

Denmark is one of several countries cracking down on trading schemes that reaped billions of dollars by claiming duplicate refunds on dividend taxes. Germany, Belgium and the Nordic country are all trying to extradite financial professionals in relation to the controversial strategy.

“We have had a hard time finishing because of Covid, but we expect to be done in the next couple of months,” said Fiig, whose office has grown by 100 to manage the case and a money-laundering scandal at Denmark’s biggest bank, Danske Bank A/S.

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Danish Prosecutors have three primary investigations into groups stretching from the U.S. to Malaysia that they say illegally claimed dividend tax refunds of around $2 billion.

“We are investigating, along several tracks, several people who formed a loosely knit network,” Fiig said. Regarding the other tracks, “it will take longer before our investigations show whether there are grounds for raising formal charges.”

Shah, who founded a London hedge fund that specialized in Cum-Ex trades, was one of two Britons charged earlier this month. Prosecutors allege he was the central figure in the $1.6 billion arm of the scam that hit Denmark.

Now living in Dubai, Shah has said he’ll show up in court to prove his innocence. Still, Fiig said the agency is working with “all the tools we have” to ensure that the suspects, whom SOIK declined to name, “stand before a judge.”

A spokesman for Shah reiterated his contention that “the trades were legal and he received professional advice to that effect.” Shah faces a sentence of as long as 12 years in prison.

Read More: Hedge-Fund Manager Shah Doesn’t Want to Be a Cum-Ex Fugitive

Cum-Ex was a trading strategy that used the rapid trade of shares to claim ownership and thereby become eligible for tax refunds. The practice, named for the Latin term for “With-Without,” seemed to allow multiple investors to claim refunds on a dividend tax that was paid only once.

Because of the case’s size and complexity, there’s been international collaboration since 2016 between the U.K., Germany, Belgium, and Denmark which headed the joint effort, Fiig said. Europol has also been involved, and U.S. authorities are participating as observers.

Germany has already held a trial related to Cum-Ex, winning the conviction of two investment bankers who organized the trades. And Belgium is seeking the extradition of one trader from London to answer questions related to a 22 million-euro ($26.7 million) tax fraud.

Read more: Why ‘Cum-Ex’ Tax Dodge Casts Shadow on Global Banks: QuickTake

There’s a 10-year statute of limitations on the crimes in Denmark, so prosecutors have “at least until 2022 and perhaps as late as 2025” to file preliminary charges, Fiig said.

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