More than 20 British medical students at a Sudan university have abandoned their studies and joined the Islamic State in Syria and Iraq.

The students, mostly children of medical professionals from the U.K., appear to be among the largest group collectively recruited by ISIS, according to an investigative report by Britain’s Sunday Times.

The recruits, including three sets of siblings as well as five women, were enrolled at Sudan’s University of Medical Sciences and Technology in Khartoum studying to be doctors, dentists and pharmacists.

Most of the students were of British-Sudanese origin.

Sudan is one of seven countries named under a travel ban to the U.S. by US President Donald Trump, just weeks after the outgoing Obama administration had said it would lift sanctions against the North African nation in response to the country’s fight against the Islamic State and other terrorist groups.

British authorities believe the recruits entered Islamic State territories in phases beginning March 2015, and most have been deployed by ISIS in medical facilities controlled by the group in Raqqa and Deir Ezzor, Syria and Mosul, Iraq.

In total, 27 UMST students and graduates are believed to have joined ISIS with at least six reported dead. Four or five of those are believed to have been from the British contingent according to The Times.

British intelligence agencies are combing through the social media profiles belonging to the jihadis amidst concern that some of the medics could be coordinating future attacks in the U.K.

At least two of the students had established a connection on Facebook with a convicted British jihadi Suhaib Majeed, who was found guilty last year of attempting to carry out a series of ISIS-orchestrated plots in the U.K. aimed at killing soldiers, police officers and civilians.

Majeed, 22, along with co-conspirator Tarik Hassane, also 22 and a former medical student in Sudan dubbed “the Surgeon,” were found guilty and sentenced to life in prison.

Several of the Sudanese recruits were also connected on social media with Mohammed Fakhri Al Khabbas, a British Palestinian who also attended UMST and is believed to have played a major role in facilitating recruitment for the Islamic State at the university.

Al Khabbas, led the university’s Islamic Cultural Association or ICA, using his role to invite radical preachers to events on campus and prompting British authorities to send a delegation to the university in attempts to stem further recruitment.

Khabbas is now believed to be in Raqqa, from where he has penned several essays encouraging Muslims to make Hijrah and journey to the Caliphate.