An official says the suspicious powdery substance that was sent to six consulates in Istanbul, leading to the hospitalization of more than 30 staff members, was a material similar to chalk dust.

Health Ministry Undersecretary Eyup Gumus said Tuesday that the powder tested negative for biological and toxic agents.

The consulates of Canada, Belgium, Germany, France and the United States were sent envelopes containing the powder Friday, leading to the evacuation of some of the missions and the hospitalization of 25 staff. The Hungarian Consulate received a similar package on Monday and six staff members were hospitalized.

Gumus said the 25 were discharged Monday after authorities determined that the material was non-toxic. Six Hungarian consulate workers were being released Tuesday.

Turkish authorities are investigating, and no arrests have been made.