Southeast Asian nations stepped up pressure on Indonesia to ratify a treaty aimed at curbing cross-border smog pollution triggered by smoke from forest fires in the country.

The recent haze problem which shrouded neighboring Malaysia and Singapore in hazardous smog prompted the two nations to raise a red flag on the issue following days of choking pollution in their cities.

Members of the Association of Southeast Asian Nations called for cooperation “to tackle the transboundary haze pollution problem” and stressed each country’s “international obligations” during the annual ministerial meeting in Brunei.

The bloc urged Indonesia, the only member which is still not a signatory of the 2002 ASEAN Agreement on Transboundary Haze Pollution, to “expeditiously” ratify and operationalize the treaty.

The agreement binds signatories to “respond promptly” to the crisis by providing information and mutual help to affected countries. It also requires parties to take preventive measures.

Indonesia Foreign Minister Marty Natalegawa said the treaty had been resubmitted to the current legislature, although no timeline for ratification was given, reports AFP.

This comes as Indonesian police arrested 14 people in connection with the forest fires in Sumatra island. Authorities have yet to establish whether companies paid the suspects to start the fires to clear the land for palm-oil plantations.