Reuters reports: U.N. war crimes investigators know of 14 potential chemical attacks in Syria since they began monitoring Syrian human rights abuses in September 2011, the team’s chairman said on Monday.

“We are investigating 14 alleged cases of chemical weapons or chemical agent use. But we have not established the responsibility or the nature of the materials that were used,” Paulo Pinheiro, chairman of the U.N. Commission of Inquiry on Syria told a news conference.

“We don’t have to share where, or when, or what moment. We don’t have to elaborate more on that.”