The envoy of the United Arab Emirates (UAE) in Iran has been summoned by Iran’s Foreign Ministry over the Oct. 7 arrest of nine Iranian teachers, reportedly due to visa issues.

Khalilollah Babalou, head of international affairs and schools abroad for the Education Ministry, told Tasnim News Agency that the UAE arrested the teachers because they only had visas to work in Dubai. At the time of their arrest they were working in Al Ain, a city in the emirate of Abu Dhabi. According to Babalou, teachers working at Iranian schools outside of their visa stipulations has not resulted in arrests before. Babalou added that Iranian officials are tyring to secure their freedom and consultations in Iran are taking place.

With nearly half a million Iranians living in the UAE, the arrests mark a troubling sign as they could spell increased tensions between the two countries. While Iran has had a good relationship with the Emirate of Dubai, particularly in trade, tensions with Abu Dhabi have been high in recent years, especially as Abu Dhabi sees itself more aligned with the regional policies of Iran’s rival, Saudi Arabia.

Rasoul Papaei, deputy for public relations at the Education Ministry, called the arrest of the teachers an “excuse.” He said that the UAE had issued an official license for Iran to direct Iranian schools that would operate under the Iranian Embassy in the country. Under this license, effective until 2016, Iran controls the affairs of the schools, according to Papaei.