Canada's consulate in Istanbul has called in Turkish investigators to check a suspicious package which arrived at the building Oct. 24, Anadolu Agency reported.
Security officials at the consulate in the Levent district notified the Turkish authorities after a letter containing an unknown yellow substance was detected.
A statement from the Turkish Prime Ministry Disaster and Emergency Management Presidency said a chemical, radiology and nuclear team was dispatched to the scene to inspect the package.
The Turkish body added: "The letter containing a yellow substance was examined in line with regular procedures.
"The air conditioning system was immediately shut down and people who were exposed to the package were kept in the room as a precaution."
According to information from the Canadian consulate, one person came directly into contact with the suspicious package and six other people had indirect exposure.
An official from Istanbul's Belgian consulate confirmed to an Anadolu Agency reporter that police were currently in the building.