More than 400 migrants crossed the Honduran border into Guatemala on Wednesday with more on the way, according to Guatemalan government officials. They are crossing legally but the numbers are highly “unusual” and making their way to U.S. Mexico border, the officials added.

Guatemala has a system similar to the European Union, whereby people from neighboring countries, can cross legally into the country if they have appropriate paperwork, the officials stated. However, concern is mounting that other illegal migrants from far-off nations – including nations with ties to terrorism – haveĀ also been found attempting to cross illegally into Guatemala, authorities said.

“More than 300 to 400 people have entered Guatemala in the last 24 hours,” said the official.

Many Honduran migrants arrived by bus to the Guatemalan border, officials said. The migrants paid for the bus trip but the bigger question remains, “how are they getting organized,” said the official. He said Guatemalan authorities are investigating the new surge and working closely with U.S. counterparts.