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As authorities in rural West Texas continue to seek an unknown gunman who fired on four U.S. workers from Mexico last week, some local politicians and state authorities say the incident is yet another example of bullets crossing the border -- a situation that is "bad and getting worse."

Hudspeth County Sheriff's Department Chief Deputy Mike Doyal said a crew of four county employees was working on a remote, unpaved road roughly half a mile from the border in Fort Quitman, Texas, when a gunman fired around eight rounds from across the Rio Grande at about 10:30 a.m. on Thursday. The workers were not injured and no suspects have been identified.

It was immediately unclear what led to the shooting, but Doyal said the area -- roughly 25 miles east of Fort Hancock and 75 miles southeast of El Paso -- is a known drug trafficking and human smuggling corridor.

"The road foreman said there had been some vehicles on the Mexican side that had been tagging them all week," Doyal said. "Whether or not they were targeted specifically, I don't know."

Doyal said the gunman may have been trying to scare the workers away from expensive equipment they were handling, or the gunman may have sought to draw attention to the area in order to smuggle drugs or illegal immigrants into the country elsewhere.

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"In years past, it has been an area where there have been spots of contention," Doyal said. "[It's] probably more drugs than anything else, but there's some human smuggling that goes on there as well."

In a Jan. 14 letter to the U.S. House of Representatives' Committees on the Judiciary and Homeland Security, Texas Attorney General Greg Abbott said the shooting was "yet another incident involving cartel-related gunfire" along the border. He called upon both committees to hold hearings to review the Obama administration's response to last week's shooting and similar incidents in the past.

In June, El Paso's City Hall was struck by at least seven shots fired from across the border in Ciudad Juarez, the epicenter of Mexico's ongoing drug war. Two months later, in August, at least one stray bullet from Mexico hit a building at the University of Texas at El Paso. In October, U.S. tourist David Hartley was reportedly shot by a Mexican gunman. And in November, the University of Texas at Brownsville temporarily canceled classes due to ongoing gunfire across the border in Matamoros, Mexico.

In an interview with FoxNews.com, Abbott said the overall state of security along the border is "bad and getting worse," particularly in south and west Texas. Only good fortune has thus far spared American lives, he said.

"We have reached out to the Obama administration to take action to protect American lives from bullets flying across the border," Abbott said Tuesday. "They have failed to respond to our call to action, so we are pursuing an alternative track to both investigate what the problems are on the border and to investigate the reason behind the inadequate response by the administration."

Asked if the Texas-Mexico border is more or less secure than it was a year ago, Abbott replied: "It grows worse by the year, almost by the month. A year or two ago, it would've been almost unheard of -- unthinkable -- that bullets would come from another country onto American soil. And now it's happened on multiple occasions."

The White House did not immediately respond to a request for comment early Wednesday.

Meanwhile, U.S. Rep. Francisco Canseco, R-Texas, said the most recent shots from Mexico are proof that the border remains unsecured.

"It is completely unacceptable that Americans at work, doing their job in America, come under gunfire from across the border in Mexico," Canseco said in a statement. "Our border is not secure from violence that threatens American lives. Securing our border against the cartels and their violent threat must be a top priority."

Bill Brooks, a spokesman for U.S. Customs and Border Protection, said agents from the 135,000-square-mile Marfa sector responded to the gunfire last Thursday. Despite the string of incidents in the Marfa sector and the neighboring El Paso sector, Brooks said security along the border is "about the same" as it was last year.

"Security on the border in the Marfa Sector is about the same now as it was in the spring of 2010," Brooks said in an e-mail to FoxNews.com. "We have been fortunate in avoiding serious incidents in our area. Our investments in personnel, infrastructure and technology are beginning to pay dividends."

Apprehensions in the sector during the first 11 months of 2010 totaled 4,964 individuals, compared to 5,879 during the same period in 2009, Brooks said. Seizures of marijuana totaled 49,996 pounds during that span, compared to 20,587 during the same period in 2009. Cocaine seizures, meanwhile, plummeted from 82 pounds in 2009 to 42 pounds last year.

In April, FoxNews.com visited Fort Hancock, a town of roughly 1,700 about 25 miles west of the most recent shooting. At the time, Joe Romero, a Border Patrol agent in the El Paso sector, was reassuring residents that violence from Mexico -- particularly from El Porvenir, just across the Rio Grande -- could spill over at any moment.

"The residents are concerned," Romero told FoxNews.com last April. "They want to know what's happening."

On Tuesday, Doyal said those concerns continue to linger.

"I don't think there's been much of a decrease," the deputy said of illegal border activity in Hudspeth County. "On our side, it's sporadic. You may go a long time without an incident, and then something pops up. The key is to keep the violence on the other side."

Doyal continued, "But what happened last week affected four families on this side. Next week, if something happens, even if it happens in Mexico and there are relatives in Fort Hancock, it's going to affect those people."