The nation’s southwest border is in "crisis," with authorities stopping between 1,500 and 1,700 illegal entrants a day, Secretary of Homeland Security Kirstjen Nielsen said Sunday.

In an interview on "Fox News Sunday," Nielsen called the massive caravan of refugees from Central America just "one iteration" of the flood of illegal immigrants at the border.

"We have a crisis at the border right now,” she said. "We are stopping between 1,500 and 1,700 people a day trying to cross illegally into this country. This caravan is one iteration of that but frankly, we eventually see caravans every day with these numbers."

Nielsen called a caravan currently making its way north as one having a "moment-to-moment" membership.

"This isn't a ticketed event if you don't have a membership in the caravan,” she said.

“There are consistently moment to moment folks raising a hand saying they are part of the so-called caravan and then there are others who yesterday said they were part of the caravan, today say they are no longer a part of the caravan. What we are really talking about is the flow of people that are headed towards the United States. They have chosen to break laws along the way. "

Nielsen said she doesn’t “know everybody in this flow,” and that terrorists try to enter the country via the southwest border.

“We stop 3,000 people a year who have travel patterns similar to terrorists attempting to come in the southwest border,” she said.

Nielsen also addressed the slaughter of 11 Jewish worshipers at a synagogue in Pittsburgh on Saturday — and that the Department of Homeland Security had provided a “protective security adviser” on a visit to the facility last March.

“This was a pure act of evil,” she said, adding: “We all condemn this in the strongest terms possible and as you know we do an extraordinary amount of planning and training for active shooter events as well as protection of soft targets in general.”

“As recently as March we actually conducted a site visit there with our protective security advisor in the area,” she said. “This is something we often do."

This story has been corrected from a previous version that stated the number trying to cross per day at 150,000.