The head of the FBI told reporters in San Antonio that there is no evidence that Middle Eastern terrorists or other individuals who are attempting to harm the United States are among the wave of Central American unaccompanied minors and other refugees who have been streaming into Texas over the past two months, Newsradio 1200 WOAI's Michael Board reports.

  "It is a possibility, and one that we have to worry about, but I am not standing here saying it is keeping me awake at night," FBI Director James Comey said.

  Comey was in San Antonio to meet local FBI agents and review operational activities in the San Antonio area.

  Comey says the FBI remains the most concerned about so called 'Lone Wolves,' radicalized American citizens who are already in the U.S., individuals like former Army Maj. Nidal Hasan, who killed 13 soldiers at Ft. Hood in 2009.

  "We are tracking more than a hundred Americans," he said.  "It is very difficult because they don't come from any particular area in the U.S., no particular demographic background."

  He says the FBI has checked up on reports that people with ties to terror have been using the Central American refugee crisis to slip into the U.S. and so far, they have found no evidence.

  "One of our obligations is to spot anybody who would do us harm coming across the border, especially those who are bent on terrorism," he said.  "So far, we haven't seen it."

  Comey said the best advice has been what the FBI has been saying since 2001..if you see something, say something.