Screen shot of Egyptian security forces squaring off against protestors in Cairo, Egypt, July 8, 2013. Photo: CBS News.

Late last month, as millions of protesters converged in Cairo’s Tahrir Square and other Egyptian cities demanding President Mohamad Morsi’s ouster, tens were killed and hundreds injured, many of them by pro-Morsi gunmen firing into crowds (one such volley can be heard in video footage of a protest in Assiut, where four people were killed). Rumors began circulating that some of the shooters were Syrians and Palestinians paid by the Brotherhood to disrupt the protests.

There is growing evidence that the rumors are true. On July 6, the Central Cairo Prosecution announced that it had a Syrian national in custody, Mohamed Hassan al-Berdkany, who was arrested a day earlier while firing birdshot at protestors from Qasr Al-Nile bridge leading to Tahrir Square. Berdkany, who fled with his family from Syria after the start of its civil war, admitted to receiving cash and a shotgun from the Brotherhood. He named another Syrian, Ahmed al-Soury, as a key figure recruiting Syrians to join Brotherhood protests. He also identified a Palestinian, Bassel al-Feroun, as responsible for paying Palestinians to take part.

Little information about the investigation has been made public, and it is not clear how extensive foreign involvement in the Egypt crisis has been or whether senior Brotherhood leaders signed off on it. Nevertheless, Egypt’s new interim government appears to be taking the threat very seriously. The Interior Ministry released a statement advising Arab expatriates to avoid demonstrations, ostensibly for their own safety. On July 8, authorities issued a decree requiring Syrian nationals to obtain a visa and security permit before entering the country (under Morsi they were allowed in unconditionally) and began enforcing it a few hours later by deporting 276 Syrians who had just arrived from Damascus and Beirut.

The concern seems to be that Syrian refugees in Egypt (more than 77,000, according to UNHCR; otherestimates put the number at over 150,000) constitute a ready pool of recruitment for Islamist provocateurs eager to maintain plausible deniability. Most are relatively poor Sunni Muslims, have no prior connection to the Brotherhood infrastructure in Egypt, and are concentrated in urban areas where major protests take place. They are generally sympathetic to Morsi, who went to bat for them in June by closing the Egyptian embassy in Damascus and calling for a no-fly zone in Syria, despite the fact that there is less (and less intense) popular support for the rebels in Egypt than in many other Arab states (evident from polling and the breakdown of non-Syrian Arabs killed fighting for the rebels).