Fearing an influx of immigrants and terrorists infiltrating the country, Bulgaria is building a 100-mile fence on its border with Turkey, where refugees and militants with the Islamic State group in Syria and Iraq cross over for safety or to smuggle weapons and foreign fighters, the New York Times reported Monday. But experts disagree on the extent of the security problem posed by the fighters.

“Right now, in the western part of Turkey, on the borders of Greece and Bulgaria, you probably have thousands of Syrian refugees waiting for an occasion to cross,” Marc Pierini, a Turkey and Middle East expert at the foreign policy analysis group Carnegie Europe, told the Times. “If you talk about returning jihadists, you are talking about dozens.”

Bulgarian security expert Slavcho Velkob said authorities were underestimating the number of jihadists trying to enter Bulgaria. “I have seen such fighters here with my own eyes,” he said. “I spotted some at the central bus station and struck up a conversation. When I asked them where they were going, they said, ‘We are going to heaven.’ ”

The crisis in Syria has led to tens of thousands of refugees fleeing for Europe. About 200,000 entered Europe through land and sea in 2014, according to the Times. And that figure doesn’t count the refugees that evaded authorities.

Bulgaria shares a 100-mile land border with Turkey. In September, a 20-mile section of the border fence was completed. European officials are worried that warmer weather will bring a surge of refugees from war-torn areas to the continent.

In keeping migrants out, Bulgaria, the poorest country in the European Union, is also hoping to fix economic woes caused by the influx of immigration. The refugees put a strain on resources that has led to a rise in anti-immigrant sentiment throughout Europe in the form of far-right political parties. “The rise of the right wing in Europe is a reaction to this refugee flow,” Bulgarian U.N. spokesman Boris B. Cheshirkov told the Times.

The border fence is just one part of Bulgaria’s plan to stanch the flow of immigrants. The country has also added more border security personnel and given them new surveillance equipment to detect illegal immigrants.