A report in the British media that Turkey handed over two Britons fighting for ISIS to the militant group in exchange for Turkish hostages has been deemed “credible” by the British government, the BBC reported Monday. The swap was made last month, but it was first reported in the Times of London on Monday.

Britons Shabazz Suleman, 18, and Hisham Folkard, 26, were among the 180 ISIS militants exchanged for 46 Turkish hostages who worked at the Turkish consulate in Mosul, Iraq, according to the Times report. A former classmate of Suleman’s claimed the 18-year-old jihadist sent him a message on Twitter that read, “I’m in Syria LOL. Doing aid work,” according to the Daily Mail.   

Less is known about Folkard. His father, a Roman Catholic, told the Times that he had little contact with his son, who he said was taken away by his mother. He said he cut off contact with his son after his mother allowed him to study Islam in Yemen.

The Times said it saw a leaked list of the names involved in the prisoner swap and that Suleman and Folkard were on it. A British government source told the BBC that the Times report was “credible.”

The United Kingdom says it doesn’t negotiate with terrorists, but it is unclear how much of a role the U.K. played in the exchange. Turkish President Recep Tayyip Erdoğan called the swap a “cover operation,” according to the Independent.