An American woman isn't being identified by as a suspect in her husband's death on a Mexican border lake, U.S. investigators said, tamping down speculation about the credibility of her story.

U.S. law enforcement officials said Thursday that they have undisclosed "information" leading them to believe Tiffany Harley had no criminal involvement in an alleged attack on her husband on Lake Falcon, a 60-mile-long lake that connects Texas with Mexico.

Sheriff Martin Cuellar of Webb County said Thursday that authorities have information suggesting Hartley's story is credible. Hartley of Milliken, Colo., said her husband, David, was shot by Mexican pirates on the lake last week as they were returning to the United States on Jet Skis. 

"Information has surfaced that we can't disclose at this time that she didn’t commit any kind of offense," Cuellar told reporters. 

Hartley has said she tried to pull her husband's body from the water after he was shot in the back of his head but was unable to. The 29-year-old woman told authorities she fled the scene for fear that Mexican bandits would shoot her.

No body has been recovered and Mexican authorities, meanwhile, have questioned Hartley's account, saying there's no evidence indicating that a crime was committed. 

On Wednesday, Cuellar sought to dispel such suggestions. He told reporters "there is indication of blood on her vest," and he suggested that the blood -- which he didn't immediately identify as David Hartley's -- got onto his wife's vest as she was trying to lift him from the water. 

Rep. Henry Cuellar, the sheriff's brother, also said that a "reliable" eyewitness on the U.S. side of the lake saw Tiffany Hartley being chased back to shore by an unknown boat.

"A person did see her coming in with a boat chasing her," the lawmaker told reporters. 

Mexican authorities said they began searching the border lake Wednesday for Hartley's body -- almost one week after the 911 call from his wife reporting the alleged shooting. 

The Mexican Foreign Ministry said Wednesday they have been coordinating a search "from the first moment" that Hartley reported Mexican pirates shot and killed her husband as they were riding Jet Skis across the lake last week. But Rios' comment suggests the search didn't begin until Texas Gov. Rick Perry called Mexican authorities late Tuesday to demand more action.

Ruben Rios, spokesman for Tamaulipas state prosecutors, said the search was suspended at 5 p.m. Wednesday because of bad weather conditions and was resumed Thursday morning.

Rios says authorities have been looking by air and in the lake, but he says, "so far they have found nothing."

U.S. officials also said Thursday that the search has also been hindered because of threats of an ambush on the lake.

"There is a threat. There is a drug war going on in Mexico," Sheriff Sigifredo Gonzalez of Zapata County said during the press conference. 

Perry said Wednesday he has asked Mexico's president to call him in the next 48 hours to say that the body of an American reportedly shot to death on a border lake has been recovered.

There is no word yet on whether such a call has taken place. 

Rep. Solomon Ortiz said Thursday that Mexico is fully cooperating in the search to recover Hartley.

"There's no doubt that we see this as a cooperative effort," he said.

The U.S. State Department said in an e-mail sent to Thursday that: "Mexican authorities are engaged in the search effort and the U.S. government has offered our assistance in that search."'s Cristina Corbin and the Associated Press contributed to this report