The Turkish Islamist group IHH is under investigation for allegedly funding global terrorist network Al-Qaeda, Turkish media outlets have reported.

IHH President Bulent Yildirim has been accused of funding the terrorist group secretly, without official documentation. Two Turkish special prosecutors are conducting separate probes into the allegations.

Yildirim was the head of IHH in 2010 when the group funded a “flotilla” aimed at breaking Israel’s naval blockade of Hamas-controlled Gaza. Dozens of far-left American and European activists joined the cause.

One of the boats in the flotilla, the Mavi Marmara, refused to turn aside when ordered to, attempting instead to break the blockade by force. When IDF soldiers boarded the ship they were violently attacked. Soldiers opened fire in response, killing 9 Turkish activists.

The incident caused Israel’s relationship with Turkey, already strained, to break down completely. Turkish leaders demanded an apology, but Israeli leaders refused, saying Israel had acted in self-defense.