WASHINGTON – Federal officials have provided conflicting accounts for why a Mexican man with a dangerous strain of tuberculosis was able to cross the border into the U.S. multiple times this spring, two senators said Wednesday.

Last week, Homeland Security Department officials said the man was able to evade Customs authorities because U.S. officials were not provided with his real name. But Tuesday night, the department told Senate aides the Mexican man used his middle and two last names.

“I have absolutely no confidence that we have gotten all of the facts yet, nor that DHS has a good handle on how this could occur,” Sen. Susan Collins, R-Maine, said in an interview.

“That sounds significant alarm bells in terms of our confidence that this system can help us detect and disrupt the travel of those who would do us harm deliberately.”

Collins and Sen. Joe Lieberman, a Connecticut independent, want an investigation into that incident.