WASHINGTON – Homeland Security Secretary John Kelly warned that the U.S. must secure its borders to prevent a bad actor from smuggling a biological weapon into the country.

When asked if terrorists attempting to cross the border are a concern for DHS, Kelly said an “increasing number” of “special-interest aliens” are being picked up for attempted illegal crossings.

“Anything that wants to get into the United States can through that network – drugs, hundreds of tons, here I’m talking hard drugs, but hundreds of tons of methamphetamine, heroin and cocaine ride that networking into the United States in a nearly unstoppable way,” Kelly said on Wednesday during the Center for a New American Security (CNAS) annual conference, “Navigating the Divide.”

“Terrorists, I’m fairly confident right now they are not riding that network,” he added. “We do pick up, the United States, our Mexican partners, Central American partners, are picking up an increasing number of individuals here, special-interest aliens, that travel from other parts of the world at great expense to come into the country. Typically people that spend that kind of money are not coming here to drive a taxi in Washington, D.C., or to wash dishes; they are coming here for another reason. But right now we are actually very, very good at locating them and sending them back before they ever get into the United States.”

SIAs originate from countries such as Afghanistan, Iran, Iraq and Pakistan.

Kelly explained the U.S. attempts to stop illegal drugs and illegal crossings with a variety of tools.

“We stop it with technology, we stop it with physical barriers. They work, and we are working towards that, but we also stop it with working very, very closely with our partners’ passenger information exchange and just being shoulder-to-shoulder with them, and it does work,” he said.

Kelly stressed the importance of securing the border to prevent the smuggling of weapons.

“Perhaps least likely, I hope, but the biggest catastrophe would be an atomic device of some type smuggled into the country or a biological weapon that set off a pandemic. That’s why, again, not to go down this road too early in the conversation, but that’s why securing our borders is so important and we are doing that already working with our partners to the south and to the north – working all around the world with our partners that send commercial shipping to our country, but it’s vitally important to secure our borders and the homeland,” he said.

Kelly emphasized the importance of working relationships between mosques and churches with police departments so they can report individuals who “spout” hateful and extreme rhetoric before they might try to carry out any terrorist attacks.

“At the end of it all, it’s just a small number of people that go down this road. The overwhelming number of Christians, Jews, Sikh, Muslims are good people, and we should never ever forget that,” Kelly said.

Kelly referred to a neighbor who told the media he did not report one of the San Bernardino terrorists because he did not want to risk being taken to court for “slander.”

“I think I would err on the side of caution if I was a neighbor,” Kelly said. “I think it’s something that’s the reality of the time we live. If you see something, say something.”