It’s possible ISIS members have entered the U.S. through its border with Mexico, according to Texas Gov. Rick Perry.

After a speech Thursday co-hosted by the Heritage Foundation and National Review, one attendee asked the governor if he thought ISIS terrorists had crossed the southern border.

“We’ve seen historic high levels of individuals from countries with terrorist ties over the course of the last month,” he said.

“I think it is a very real possibility that they may have already used it,” he added, speaking of members of ISIS. He also said there’s no clear evidence that ISIS actors have entered the U.S. through the border with Mexico.

He added that three Ukranian individuals were apprehended at a West Texas ranch in the last 60 days.

In his speech, the governor placed blame for the border crisis on President Obama's “willful neglect of clear presidential responsibility.

“We have a crisis on our southern border that is entirely within the power of the president to deal with under the law,” Perry said.

He charged that the president’s failures to consistently enforce immigration laws have directly resulted in the recent influx of thousands of children from Latin American countries.

“When laws are treated this way, what usually follows are chaos and grief, and that’s exactly what we’ve got right now,” he said.