Washington (CNN) -- Do Mexican drug cartels have scores of "spotters" sitting on Arizona mountain tops helping drug couriers make their appointed rounds?
Two government officials -- both of whom say they've been briefed on the topic -- have vastly different claims on that subject.
Sen. John McCain, R-Arizona, said he was told in two briefings that between 100 and 200 spotters are "sitting on mountains in southern Arizona -- inside the borders of the United States of America -- spotting for drug cartels."
"That is not my assessment of the situation; it was an assessment given to me-- 100 to 200 spotters sitting on mountains," McCain said. McCain said he was briefed by the Arizona HIDTA, or High Intensity Drug Trafficking Area, a local, state and federal task force.
But Department of Homeland Security Secretary Janet Napolitano said McCain is mistaken.
"I've asked the Border Patrol... 'Where are the spotters that I keep hearing about?' And the answer I receive is there are a couple of hundred tops from which a spotter can act. But they are not sitting there, 200 drug spotters."
Napolitano said the government is "deploying technology" to enable it to pick up drug traffickers. "So I'd really be interested in seeing if we can clarify that particular point," she said.
Not persuaded, McCain started to say it was "crazy" for Napolitano to deny the existence of the spotters, but cut himself short. "Look, they are there and everyone knows they're there and for you and your staff to deny that they're there is sort of symptomatic to me," McCain said.
The exchange took place Wednesday at a Senate Homeland Security Committee hearing.
A representative of the Arizona HIDTA, contacted by CNN, declined to answer any questions, referring calls to DHS public affairs.
A Homeland Security official, speaking on background, said U.S. Customs and Border Protection officials, as part of regular enforcement operations in the Tucson, Arizona, sector, identify and document possible scouting locations so they can monitor them and prevent their use by spotters or scouts.
"This information is distributed to agents working in each specific area," the official said. "This information does not indicate that all of these scouting locations are being occupied by Mexican drug cartel members."
In July, a Mexican national was arrested after a pilot spotted him at a peak overlooking Silverbell, Arizona. The man, who was not in the U.S. legally, was living in a cave, and had a supply of food, clothing, communications equipment and binoculars, according to the Pinal County, Arizona, sheriff's office.
But because it is not illegal per se to stand on a mountaintop with binoculars, agents could do little other than deport him, authorities said.