* Singapore's main wealth fund GIC invests 93 mln euros
* GIC could invest further 474.2 mln euros
* Sintonia holding ups stake in Italy toll road operator
MILAN, June 21 (Reuters) - A unit of Singapore's main wealth fund has raised its stake in the holding company which controls Italian toll road operator Atlantia (ATL.MI), allowing it to boost its Atlantia ownership to 43.21 percent.
Infrastructure holding company Sintonia said in a statement on Tuesday a unit of the Government of Singapore Investment Corporation (GIC) had financed a 92.6 million euro capital increase which allowed Sintonia to buy a further 0.96 percent of Atlantia last month.
Following the move, the stake of GIC's Elmbridge Investment Pte Ltd in Sintonia rose to 8.92 percent, the company said in the statement.
The stake could rise further to 17.68 percent, the statement said, as the board of the holding company could decide further capital increases reserved to Elmbridge Investment for up to 474.2 million euros ($680.2 million).
The Italian press has speculated in recent weeks about a possible breakup of Sintonia. A source close to the company said the latest move highlighted shareholders' commitment.
"It's a sign shareholders are committed after all the talk about a possible breakup," the source said.
Edizione, the holding company of Italy's Benetton family, is the chief shareholder in Sintonia with a 73.46 percent stake which would fall to 66.4 percent when the capital increases reserved to Elmbridge Investment are carried out. ($1=.6971 Euro) (Reporting by Valentina Za, editing by Dave Zimmerman)