(CBS) Zapata County's sheriff Sigifredo Gonzalez has told CBS News he has blood evidence from the lifevest of Tiffany Hartley, the wife of David Hartley, that supports her account of a pirate attack on a lake that straddles the Texas-Mexico border.

CBS News correspondent Don Teague reported on "The Early Show" this evidence is in addition to witness testimony that supports Tiffany Hartley's story that her husband was shot in the head by pirates on Mexico side of Falcon Lake.

David Hartley is presumed dead, and officials on both the U.S. and Mexican sides of the lake are searching for his body.

Gonzalez told Teague he believes the Hartleys were attacked by enforcers of the Zeta drug cartel. The Hartleys, Gonzalez says, were innocent victims of a bloody drug war.

Escorted by heavily armed federal agents, CBS News took a boat ride to the border with Gonzales Thursday.

Gonzalez said, "There are problems along the border. Whether you admit it or not there are problems and it's spillover violence."

The sheriff's objectives were to show that the American side of Falcon Lake is safe, and to deliver a message to the drug cartel that controls the water, and land beyond the border.

Gonzalez said, "What I've told them is, 'I need a body. Give me a body, guys, and everything will go away. Give a body guys and the news media will go away.'"

Gonzales fears the same cartel enforcers who killed David have permanently hidden his body.

He said, "The body has been disposed of. They have it somewhere they've gotten rid of the body so there's no evidence."

But that's not something Tiffany Hartley is ready to accept, and says she's only now beginning to grieve.

Tiffany Hartley said, "At certain times there's points where you do feel like this is it. I'm never gonna see him again. He's gone. And then at other points he's gonna be walking through that door."

Doubt has been cast on Tiffany Hartley's story by Mexico officials, but she told CNN recently she would take a lie detector test if people continue to doubt her account of the attack.

Teague added on "The Early Show" that search for David Hartley's body in cartel-controlled waters is so dangerous for Mexican authorities, they had to briefly suspend searching for a time on Wednesday. He added, the good news, there has been no report of any actual violence against searchers and the search was back on Thursday and expected to begin again Friday.

On "The Early Show" Congressman Ted Poe, (R-Texas), who has been involved extensively in this case as well as ongoing border issues, said he has requested from the State Department that Americans search the Mexican side.

He said, "The Mexican government said yes, then backed off and said, 'No, we don't want the Americans over here.' We need to use the American resources that we have, because that area of the lake is controlled by the Zetas, there is an island on that lake where the Zetas really operate, the drug cartels. If we mean business about trying to recover David Hartley's body we need American involvement and the Mexican government needs to be relentless to find it. They are intimidated now, they really won't go near the area where the Zetas operate."

"Early Show" co-anchor Harry Smith said, "We need to stop and pause a second because even the Mexican authorities themselves are clearly not in control. It's the drug cartel that is in control becausethe Mexican authorities backed away when they were threatened."

Poe agreed, saying, "That area of Falcon Lake on the Mexican side, all the way to the American edge of the water is controlled by the Zeta cartels. They bring those drugs into the United States, usually at night by high-speed boats, and they operate -- that is their operation -- and the Mexican government hasn't been able to stop them, won't stop them, refuses to or cannot, whatever the situation is, and they control that area. The government, neither government, controls that area, the drug cartels. And we're being held really hostage by the drug cartels on that area of the lake."

Smith added that while there has been some doubt cast on Tiffany Hartley's story, this is not the only reported incident of violence on this lake.

Poe replied, "American fishermen, fishing both on the American side of the lake and on the Mexican side of the lake -- you can get a permit to do that -- have been robbed by pirates on the lake, some of them have been taken to the Mexican side, stripped of all of their clothing and their valuables and their boat and left stranded there. This is the fifth time since May there's been some type of violence -- but the first homicide."

Poe said he'd like to see the United States to have more involvement in the search.

The United States needs to use our resources