ISIS has reportedly developed high powered explosives that can be hidden inside laptops and are entirely undetectable by regular airport scanners.

CBS News reports that following the discovery of equipment left behind by ISIS fighters at the University of Mosul in Northern Iraq, the US government believes that sophisticated new bombs could be concealed within laptop computers and may be much harder to detect by traditional airport security scanners. After Iraqi special forces recaptured the University of Mosul in January, it was discovered that ISIS had used the university’s equipment and laboratories to develop these new explosives.

ISIS bomb makers reportedly tested how easily detectable the new explosives are by modern security screenings by using airport scanners that they stole from the Mosul airport after the Islamic extremist group overran the city in 2014. Following the retreat of ISIS troops as they were routed by US troops in January, the terrorist group burned any areas that they had occupied, but enough was recovered to determine the type of explosives that the group was developing.

It was the discovery of these explosive devices that lead to serious discussion about whether or not to ban laptops on flights from the UK and Europe to the United States. However, on Wednesday it was decided not create such a ban yet, and a promise between US and EU officials was made to increase the sharing of intelligence between the two groups. Airlines had strongly opposed the proposal, outlining how the new security measure would lead to a decrease in trans-Atlantic air travel.

As many as 65 million people a year travel between Europe and North America, with nearly 400 flights a day crossing the Atlantic with many business travelers onboard who require their laptops and electronic devices in order to do their jobs. This ban would be much larger than the current electronics ban which was put in place in March and affects about 50 flights per day from 10 cities, mostly located in the Middle East.