Aya Fadl, lies on a bed, with an oxygen mask to heal breathing difficulties following a suspected chemical attack on her town of Khan Sheikhoun, in the northern province of Idlib, Syria, Wednesday, April 5, 2017.

:: The United Nations is working to obtain security assurances needed to dispatch an international team of experts to the site of last month’s suspected sarin gas attack in Syria, a UN official said Tuesday.

At least 88 people died in the April 4 alleged attack at Khan Sheikhun, in rebel-held Idlib province, which the United States and its European allies blame on Syrian government forces.

UN disarmament chief Izumi Nakamitsu told the Security Council that planning for the fact-finding mission to Khan Sheikhun was “already underway,” but no date has been set.

The team from the Organization for the Prohibition of Chemical Weapons (OPCW) would deploy to an area under opposition control to collect samples and testimony from witnesses.

Nakamitsu said she was working to “help ensure that any visit to the site by the FFM (fact-finding mission) team will be accompanied by the most stringent security assurances.”

Samples taken from victims, wounded patients and dead animals from Khan Sheikhun have tested positive for sarin or a sarin-like substance, the OPCW has told the council.

Samples were taken from three victims during autopsies, ten individuals who were treated at hospital, two birds that were contaminated as well as soil and vegetation, the UN body said in a report to the council.

Ahmet Uzumcu, the OPCW’s director general, said last month that the “incontrovertible” test results showed sarin or a similar substance had been used.

In a separate report to the council, the OPCW said two Syrian women were exposed to sulphur mustard in a suspected attack in September 2016 in Um Hosh, in the Aleppo countryside.

The fact-finding team was not able to visit the site of that apparent attack.

The two reports will be handed over to the joint UN-OPCW investigative panel (JIM) which is tasked with attributing blame for the chemical weapons attacks in Syria.

In previous reports, the JIM found that Syrian government forces were responsible for chlorine attacks on at least three villages in 2014 and 2015, and that ISIS used mustard gas in 2015.

Russia, Syria’s ally, has dismissed the findings as not credible. In February, Moscow vetoed a UN resolution that would have imposed sanctions on Syria over chemical weapons use.

Nakamitsu said the “re-emergence” of chemical weapons was “indefensible” and stressed “this is not an issue to be politicized.”