A global chemical weapons watchdog have released an interim report stating that "various chlorinated organic chemicals" were found at the site in Syria where a chemical attack is suspected of being carried out in April.

Key points: So far "no organophosphorus nerve agents" were detected

So far "no organophosphorus nerve agents" were detected OPCW warned that it was too early to come to conclusions

OPCW warned that it was too early to come to conclusions Russia and Syria have sought to disprove that Douma was hit by a poison gas attack

A fact-finding mission by the Organisation for the Prohibition of Chemical Weapons (OPCW) warned it was too early to come to conclusions about the suspected attack on the town of Douma, saying "work by the team to establish the significance of these results is ongoing".

At the same time, the investigators reported, based on initial results, that "no organophosphorus nerve agents or their degradation products" were detected in samples taken from people allegedly exposed or in the environment.

The OPCW is investigating the suspected April 7 chemical attack on Douma, a town near the Syrian capital, Damascus.

The United States, Britain and France blamed Syrian Government forces and launched punitive airstrikes. Syria denied responsibility.

The chemical weapons organisation, based in the Netherlands, does not designate blame for chemical attacks.

The team said in its report that it found two industrial gas cylinders at different locations in Douma — one on a top-floor patio and the other on a bed in a top-floor apartment.

It said it is working to establish how they got there and whether they are linked to the alleged attack.

More time needed for investigation

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The team said it "needs to continue its work to draw final conclusions regarding the alleged incident and, to this end, the investigation is ongoing".

Russia and Syria sought to disprove that Douma was hit by a poison gas attack, and in April brought a group of Syrians to the global chemical weapons watchdog's headquarters in The Hague to denounce the reports of an illegal attack as fake.

The insistence by Russia and Syria that a chemical weapons attack was staged runs counter to accounts from witnesses and survivors interviewed by media, some of them in Douma, who described being overwhelmed by a strong smell of chlorine.

Some survivors interviewed in Douma after government forces took control of the town blamed rebels from the Army of Islam group of being behind the attack.

Other survivors who left Douma said the chlorine attack occurred amid government airstrikes and blamed the Government of Syrian President Bashar Assad.

AP/Reuters