Tehran and Moscow have both suggested that the international community should investigate the circumstances behind the Khan Sheikhoun deaths before responding political or militarily or even definitively ascribing the incident to forces loyal to the Assad regime.

Following the Syrian president’s talking points, his foreign allies have supported an alternative explanation that claims the given chemical agents may have been held in a rebel warehouse and released accidentally after a strike by Syrian forces. But no evidence has been presented to suggest that the rebels were capable of synthesizing sarin gas or similar chemical agents, or that they might have acquired them from outside sources. Meanwhile, the Assad regime has a well-recognized track record of using chemical weapons, having deployed sarin early in the conflict and having used chlorine gas against rebel-controlled areas several times since then.

Under an agreement brokered by the US and Russia, Assad was supposed to have given up his stockpiles of nerve agents by the summer of 2014, but a relative lack of transparency on the part of the Syrian government led to some speculation that undeclared stockpiles had been retained. And in any event, experts who have recently commented on the Khan Sheikhoun attack have pointed out that the regime had the ability to synthesize more sarin and ample time in which to do so.

In light of such observations, it is easy to conclude that the Iranian Foreign Minister’s criticisms of the US response are disingenuous and indicative of the same kind of political motives that he ascribes to the American government. And as The Tower pointed out last week, the Iranian defense of Assad in the wake of the Khan Sheikhoun attack was only part of a broader pattern of ignoring confirmed chemical attacks, barrel bombings of civilian populations, and other war crimes. The same article notes that Zarif has repeatedly attempted to deflect criticism by “playing the victim” with regard to chemical weapons and saying that Tehran would never defend such attacks, having been the target of them during the Iran-Iraq War in the 1980s.

But The Tower does more than just suggest the Iranian government is being hypocritical in its defense of Assad’s chemical attacks. It notes that there is “mounting evidence” that the Iranian regime itself has an active chemical weapons program and is worried that this will be subject to more scrutiny in the wake of a Western response to the Syrian attacks. The article pointed out, for instance, that German intelligence reports indicated that Iranian entities had attempted to acquire numerous components with applications to nuclear, biological, and chemical warfare.

The article also indicated that some Iranian Kurds have claimed that chemical weapons may have been used against them, a fact that would seriously underscore the Congressional Research Service’s recent conclusion that Tehran may be in violation of the Chemical Weapons Convention, which it ratified approximately 20 years ago.

Of course, such violations would make it all the more unsurprising if Tehran was knowingly turning a blind eye to worse violations being carried out by its Syrian ally. But regardless of the accuracy of the CRS’s conclusion or the Kurdish claims of small-scale Iranian chemical warfare, the fact remains that it is highly unlikely that Zarif or other high-ranking Iranian officials would be unaware of Syrian chemical weapons activity.

Zarif’s recent criticisms called for international investigations but failed to provide any information to contradict the Western conclusion that Assad is responsible for Khan Sheikhoun. But the Iranian government should be in a position to immediately help with the called-for investigation, given how deeply embedded the Iranian Revolutionary Guard Corps and its local proxies are among forces loyal to the Assad regime.

In fact, in an editorial published on Sunday in the New York Post, former US Ambassador to the UN John Bolton pointed out that IRGC forces were personally present at the Syrian airbase that was targeted by the US strike after having apparently been used for the deployment of airborne chemical weapons. Bolton went on to credit Tehran and the IRGC in particular with saving Assad from overthrow and subsequently buttressing his continued efforts to destroy the rebel opposition.

This is a situation that Bolton highlighted to make a case for designating the IRGC as a foreign terrorist organization and subjecting it to harsh financial restrictions. For some people, such a move was made more imperative not just by the extensive Iranian intervention in the Syrian Civil War but also by the effects of the nuclear agreement spearheaded by the previous US president. As well as providing Iran with direct relief from nuclear related sanctions, that agreement led to Western business deals with the Islamic Republic including commercial aircraft sales that some experts fear will expand connections between the IRGC, Syria, and other areas of Iranian influence.

This concern was highlighted by The Tower on Friday, in an article that claims approximately 21,000 people and 5,000 tons of supplies had been smuggled into Syrian by the IRGC is just two months’ time, using commercial aircraft. Notably, the IRGC has reportedly repurposed aircraft belonging both to Mahan Air, which remains under sanctions over such activities, and to Iran Air, which had sanctions removed as a result of the nuclear agreement. The article also points out that there are deep connections between another Iranian carrier, Aseman Airlines, and the IRGC. Both Aseman and Iran Air have entered into agreements to purchase planes from American aircraft manufacturer Boeing and European manufacturer Airbus. The Tower points out that both the Foundation for Defense of Democracies and some US lawmakers have called for the US Treasury to halt these sales until it proves that the aircraft won’t be used by the IRGC for the support of terrorist activity.

These sorts of concerns are not limited to IRGC activity in Syria, and The Tower points out that many of the flights between Tehran and Damascus have also stopped in Iraq to board Shiite militant fighters who had been operating on Tehran’s behalf there. This goes to show that the Iranian government’s defense of its allies has the potential to be mutually supportive and self-reinforcing, in line with the well-recognized Iranian ambition for the establishment of a unified “Shiite crescent” that spans much of the Middle East.

On Friday, US Senator John McCain visited Iranian Resistance offices in Albania, where he met with National Council of Resistance of Iran President Maryam Rajavi. During the visit, the senator commented upon the threat of expanding Iranian influence, tying it to the particular issue of Tehran’s defense of Assad in the midst of various apparent war crimes.

“It is a fact that Bashar Assad would not be in power today if it had not been for the Iranian Revolutionary Guards, and the Iranian help and the Hezbollah that came to Syria when Bashar Assad was about to fall,” McCain said. “There is no doubt that Iran is attempting to stifle freedom and democracy throughout the region.”