Tamaulipas State Police Commander Juan Carlos Ballesteros told El Universal newspaper on Saturday that authorities believe Juan Pedro Saldivar-Farias and Jose Manuel Saldivar-Farias killed Hartley.
Ballesteros told the paper that the two men are accused in numerous crimes in Mexico, including burning homes, robbing businesses and several homicides.
CBS Affiliate KGBT says it is clear how the men were identified as suspects, and that authorities have not released photographs of them.
On Friday the Mexican government said it had opened a federal investigation into the reported shooting of David Hartley.
A statement from Mexico's Ministry of Foreign Affairs Friday also said it "categorically rejects claims to the effect that Mexican authorities are not doing enough to find" Hartley.
Hartley's wife, Tiffany, said she and her husband were riding jet skis back from Mexico on September 30 when they were attacked by Mexican pirates in speedboats who opened fire and shot David Hartley in the back of the head.
He fell into the water of Falcon Lake, a dammed section of the Rio Grande, 25 miles long and three miles across.
Tiffany Hartley has said she tried to rescue him but fled to the U.S. side of the lake as the pirates continued shooting.
Authorities still haven't found David Hartley's body or his jet ski despite an intense search on the Mexican side of Falcon Lake. Officials report the area is a stronghold for the Zetas drug cartel.
Hundreds of people - including members of the Mexican army and federal police and state and local authorities - have been using speedboats, helicopters and all-terrain vehicles to search for him.
KGBT also reports that Mexican soldiers reportedly killed six gunmen Thursday afternoon, in the same area where Hartley went missing.