It was not immediately clear when the Belgian offer was made. But as with the French offer, made on February 14, the agency would have three weeks from that date to decide whether to accept it, sources said.
Industry sources say subsidy levels recently granted at the EU's sugar export tenders have been very low, while substantial volumes are being shipped.
The dollar's weakness against the euro has also made it more difficult for EU exporters to find world markets, they say.
Intervention offers might be justified in some cases since exporter revenues were below the EU's intervention price for white sugar, set at 632 euros ($824.5) per tonne, traders said.
Officials at the Commission, the EU's executive arm, have called the intervention offer a "highly unusual situation".
Since world sugar prices have risen over recent months, the executive has to monitor both the value and volume of subsidies to ensure that the EU's WTO export ceilings are not exceeded.