Turkish security forces have detained around 300 migrants, mostly Afghans, on Tuesday who were trying to cross into Turkey from the Iranian border, authorities said on Wednesday.

The group were found inside a large truck, including women and young children.

Concerns over a potential new influx of migrants into Turkey from Afghanistan, via Iran, have grown in recent weeks as violence between the Afghan government and the Taliban has surged as U.S. and NATO forces withdraw.

The U.N. refugee agency estimates 270,000 Afghans have been displaced inside the country since January, bringing the number of people forced from their homes to more than 3.5 million.

Foreign ministers of Turkey, Afghanistan and Iran discussed cooperation on security, energy, and migration in June but Turkish diplomatic sources say there is no specific mechanism between Ankara and Tehran to address migration from Afghanistan.