By Paul Davenport and Jacques Billeaud
NACO, Arizona — Investigators were scouring a rugged area Wednesday near the U.S.-Mexico for evidence in the fatal shooting of a Border Patrol agent, the first since 2010.
Nicholas Ivie and a colleague were on patrol in the Arizona desert when gunfire broke out before dawn Tuesday, according to the Border Patrol.
Ivie, 30, was killed. The other agent, whose name hasn't been released, was shot in the ankle and buttocks but was released from a hospital Wednesday.
It was the first fatal shooting of an agent since a deadly 2010 firefight with Mexican bandits that spawned U.S. congressional probes of a botched government gun-smuggling investigation.
No arrests have been made, but authorities suspected that more than one person fired at the agents.
No weapons have been found, according to a federal law enforcement official who spoke on the condition of anonymity because information on the search hasn't been publicly released.
An FBI official said Tuesday it might take several days to process the crime scene.
Agents and deputies were searching on ATVs, horseback and on foot with up to four helicopters overhead in a known smuggling area.
President Barack Obama called Ivie's family Tuesday to offer condolences and to express his gratitude for Ivie's "selfless service to his nation," a White House statement said.
Obama made it clear that the administration "was doing everything it could to locate those responsible."
The last Border Patrol agent fatally shot on duty was Brian Terry, who died in a shootout with bandits near the border in December 2010. The Border Patrol station in Naco, where the two agents shot Tuesday were stationed, was recently named after Terry.
Terry's shooting was later linked to the government's "Fast and Furious" gun-smuggling operation, which allowed people suspected of illegally buying guns for others to walk away from gun shops with weapons rather than be arrested.
Authorities intended to track the guns into Mexico. Two rifles found at the scene of Terry's shooting were bought by a member of the gun-smuggling ring being investigated.
Critics of the operation say any shooting along the border now raises the specter that those illegal weapons are still being used in border violence.
"There's no way to know at this point how the agent was killed, but because of Operation Fast and Furious, we'll wonder for years if the guns used in any killing along the border were part of an ill-advised gun-walking strategy," Republican Sen. Chuck Grassley said in a statement.
The Terry family said that the shooting was a "graphic reminder of the inherent dangers that threaten the safety of those who live and work near the border."
The agents were fired upon in a rugged, hilly area about five miles (8 kilometers) north of the border as they responded to an alarm that was triggered on one of the thousands of sensors placed along the border, said sheriff's spokeswoman Carol Capas.
It wasn't immediately known whether the agents returned fire, she said.
Twenty-six Border Patrol agents have died in the line of duty since 2002.
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Copyright 2012 Associated Press