ZAPATA, Texas - A search for a missing American tourist presumably shot and killed by Mexican pirates on a border lake has been thwarted by threats of an ambush from drug gangs, U.S. officials said Thursday. U.S. Rep. Henry Cuellar told reporters that Mexican authorities are doing everything they can to find David Hartley's body while trying to keep their own crews safe. "When darkness was falling (Wednesday evening), they got word that there might be an ambush," Cuellar said. "People that are trying to do their job on the Mexican side are facing a risk, they're right inside the hornets' nest. They had to suspend the search." Cuellar said the search resumed midmorning Thursday. Tiffany Hartley said her husband, David, was shot to death by Mexican pirates chasing them on speedboats across Falcon Lake on Sept. 30 as they returned on Jet Skis from a trip to photograph a historic Mexican church. Neither his body nor the Jet Ski has been recovered. Texas officials have warned boaters and fisherman that pirates frequent the Mexican side of the lake, a 25-mile by 3-mile dammed section of the Rio Grande. That part of Tamaulipas state is overrun by violence from a turf battle between the Gulf Cartel and the Zeta drug gang, made up of former Mexican special forces soldiers, and both are battling the Mexican military. Texas Gov. Rick Perry, campaigning for re-election in Houston, said such threats were no excuse. "I don't think we're doing enough. When you call off the search the way they did and give as the reason because the drug cartels are in control of that part of the state, something's not right," Perry said. "We do not need to let our border continue to deteriorate from the standpoint of having drug cartels telling whether or not we can go in and bring the body of an American citizen who was killed. That is irresponsible." Later Thursday, Jesus de la Garza, deputy attorney general, said Mexican authorities have intensified the search under orders from Tamaulipas Gov. Eugenio Hernandez, whose office had been contacted by a member of Perry's staff. He said more than 100 people were searching for the body using speedboats, helicopters and all-terrain vehicles. Divers have also been deployed, he said. Zapata County Sheriff Sigifredo Gonzalez said he has sent word to the Zetas that he wants the body returned and has no plans to prosecute. "We just want a body," Gonzalez said. "We cannot arrest anybody for what happened in Mexico, we cannot prosecute on the state level anybody for what happened in Mexico. We just want a body. I did send word to the drug cartel, the Zeta cartel in Mexico, I sent word to them unofficially. I can't tell you how but I sent word to them." Gonzalez said he has not received a response. Mexican drug gangs thwart search for body of American Proof positive that the 'inmates in Mexico are running the asylum'.