Maine’s junior member of Congress joined two Republican and two Democratic colleagues from Texas to express their concern Tuesday to Attorney General Merrick Garland about “the violence affecting United States citizens in Mexico.”

U.S. Rep. Jared Golden, D-Maine, speaks at a news conference Nov. 1, 2022, at the State House in Augusta. Robert F. Bukaty/Associated Press

U.S. Rep. Jared Golden, the three-term Democrat from Lewiston, signed a letter to Garland that insisted “the ongoing violence by cartels across our Southern border and the risks posed to American citizens is unacceptable and must end.”

Border security has become a touchstone issue in many congressional races where GOP candidates are frequently calling for beefed-up fencing and patrols along the southern border. It’s also been a big issue for Republican presidential hopefuls.

Two Republicans who have entered the race against Golden in recent days, state Reps. Mike Soboleski of Phillips and Austin Theriault of Fort Kent, each took issue with the Democrat’s stance on protecting the nation from what they see as a wave of illegal immigration. Each of them said the country’s borders are “wide open” and promised to close them if they are elected to Congress.

“Today, our southern border remains a free-for-all and a humanitarian crisis,” Soboleski said last week.

The four House members who joined Golden in writing to the attorney general — Democrats Vicente Gonzalez and Henry Cuellar, and Republicans Dan Crenshaw and Brian Babin — cited a shooting spree on Sept. 9 in the border town of Miguel Alemán, Tamaulipas, Mexico, as a particular concern.

At least four Americans, three from Dallas and one from Atlanta, were injured in the shootings, according to a Reuters report.

The members of Congress also pointed to a March 7 assault and kidnapping in nearby Matamoros that left two American citizens dead.

In light of the violent episodes, the congressional letter urged the U.S. Department of Justice “to intervene.”

“Many of us have constituents who frequently travel to Mexico on vacation, business, or to simply visit family and friends,” the letter said.

Golden, who has represented Maine’s 2nd District since 2018, and the four co-signers said they have “seen an increase in the spread of violence across the Southern border affecting Americans” and expressed concern that Mexico’s government “has demonstrated an unwillingness to do more.”

“It is time that we — under no uncertain terms — put Mexican cartels on notice and ensure that any attack on American citizens or businesses in Mexico is thoroughly investigated. The perpetrators and leaders of these organizations must be extradited, prosecuted and brought to justice in the United States,” the congressmen wrote.

“We have a duty to protect the safety and security of Americans, regardless of where they are in the world,” they said. “Many of us in Congress stand ready to help and ensure the necessary resources are available. The time to act and do more is now.”

Golden, who is running for reelection, faces a potentially tough challenge from Soboleski, Theriault or Robert Cross, the Republicans taking him on in the 2024 race who have made border security a top issue early in the campaign. The trio of GOP contenders will face off in a June primary if they each remain in the running.