(CNN) -- Authorities in the Tamaulipas state attorney general's office gave conflicting information Monday over whether authorities are pursuing a pair of suspects in the case of a U.S. citizen who disappeared during a sightseeing trip on the U.S.-Mexican border in South Texas.
While Luis Homero Uvalle, a spokesman for the office, told CNN the suspects are two brothers who are "well known to this area" -- identifying them only as "El 27" and "El 31" -- Ruben Dario-Rios, the chief spokesman for the attorney general said, "We have nothing official about suspects in the disappearance of David Hartley. I do not know where that is coming from."
Dario-Rios said the lead investigator, Rolando Flores, has not indicated that there are suspects.
David Michael Hartley went missing September 30. His wife, Tiffany, told authorities her husband was shot and killed during a sightseeing trip on Falcon Lake, which bisects the international border.
On Monday, Tiffany Hartley, along with David Hartley's mother, Pam, appeared on several morning talk shows asking for information that will help investigators find those responsible for David's death and find his body.
"Until we have him back, it's not final," Tiffany Hartley said on NBC's "The Today Show."
On Sunday, the U.S. Border Patrol, the Coast Guard, and Parks and Wildlife officials were back on the U.S. side of the lake searching for new evidence in the case, Gonzales said. Mexican authorities were searching their side of the lake as well, he said.
Authorities from both nations are conducting separate searches and are coordinating and holding regular meetings, State Department spokeswoman Virginia Staab said. But because the disappearance happened on the Mexican side of the border, the United States cannot prosecute or make arrests in the case, the sheriff said.
Tiffany Hartley was on several CNN shows Thursday recounting what happened on Falcon Lake. She also talked about her feelings about people doubting her account of the alleged attack.
Hartley said on HLN's "Issues with Jane Velez-Mitchell' that "I know what I know."
"As long as I know the truth, God knows the truth," she added. "And other than that, it almost doesn't really matter to me, because I know what happened that day."
Falcon Lake is on the Rio Grande in Zapata and Starr counties in South Texas. The U.S.-Mexican border runs through the middle of the lake.
Rep. Henry Cuellar, D-Texas, says 60 Mexican personnel, three boats and a helicopter have taken part in the search.
Despite the dangers on the Mexican side of the lake, Texas officials on Thursday said that the U.S. side of the body of water remains safe.
"It's is just as safe now as any other time. However, there is a threat," said Rep. Ruben Hinojosa D-Texas.
CNN's Justine Redman, Nick Valencia, Dave Alsup and Matt Smith contributed to this report.