Two congressmen are demanding answers from the government officials charged with oversight of US Customs and Border Protection after an ABC News investigation that shed light on a tragic 2013 episode at the U.S.-Mexico border.

Government surveillance video obtained by ABC News in partnership with The Investigative Fund shows two Customs and Border Protection officers appeared to encourage — or at least permit — a 16-year-old Mexican high school student named Cruz Velazquez to drink from a bottle that tests later revealed contained concentrated liquid methamphetamine. He died shortly afterward from acute methamphetamine intoxication.

In an Aug. 2 letter addressed to the acting secretary of the Department of Homeland Security, Rep. Juan Vargas, D-Calif., whose district includes the border crossing where the episode occurred, and Rep. Adriano Espaillat, D-N.Y., called the officers’ actions “appalling” and advocated for legislation that would rein in the agency.

“This incident is incredibly troubling and could have been prevented,” they wrote. “It also emphasizes the need for CBP and ICE [Immigration and Customs Enforcement] body cameras, as well as proper officer vetting and training. The officer’s actions toward this teenage boy are entirely deplorable and unprofessional.”

Vargas and Espaillat asked for a “detailed response” to 11 questions concerning the agency’s policies and protocols for testing suspicious substances.

“As congressional representatives, it is our duty to inquire about this incident and ensure that the matter is properly addressed in order to avoid future atrocities,” they wrote. “It is paramount that federal agents securing our border are appropriately screened and trained to safely and appropriately handle situations such as this one.”

The full text of the letter can be read below.

The Department of Homeland Security did not respond to a request for comment on the letter. Customs and Border Protection told ABC News that the agency “will respond to the congressmen directly.” In response to the initial investigation, Customs and Border Protection issued a statement saying, “CBP takes all allegations of mistreatment seriously and does not tolerate actions that are not consistent with our core values of vigilance, service to country and integrity.”

The officers in question, however, were not disciplined for their actions, and both remain on the job.

Calls for reform of the agency have gained urgency as Customs and Border Protection faces the prospect of another rapid expansion under the new administration. In a speech delivered to the Department of Homeland Security on Jan. 25, President Donald Trump issued two executive orders directing the department to hire an additional 10,000 ICE officers and 5,000 Border Patrol agents.

In July the Department of Homeland Security’s Office of the Inspector General issued a report highlighting “significant challenges” faced by the agency in following the president’s mandate, finding that, based on current hiring statistics, the agency needed a pool of 750,000 applicants to hire 5,000 additional border agents and a pool of 501,750 applicants to hire 10,000 additional immigration officers.

The need for the hiring surge is unclear, the report concluded, as “neither CBP nor ICE could provide complete data to support the operational need or deployment strategies for the additional 15,000 additional agents and officers they were directed to hire,” while critics say it could exacerbate the issues that have led to high levels of corruption in the workforce.

James Tomsheck, a former head of internal affairs for Customs and Border Protection, told ABC News that previous expansions put stress on his office’s ability to screen applicants and investigate misconduct and warned that Trump’s latest push could create similar problems.

“If it occurs at a rate that exceeds that which is appropriate to properly vet and screen applicants, it is virtually certain to allow highly unsuitable persons to enter the agency who will perpetuate the problem of corruption, misconduct and excessive use of force,” Tomsheck said.

Sen. John Cornyn, R-Texas, the chairman of the Senate Subcommittee on Border Security and Immigration, did not respond to multiple requests for comment. There are two pieces of pending legislation — one introduced in the Senate, another in the House — seeking to increase oversight of the agency.

Citing “a spike in internal corruption cases” after “the agency’s swift growth,” Sen. Dick Durbin, D-Ill., the ranking member on the Senate Subcommittee on Border Security and Immigration, introduced a bill with Sen. Tammy Duckworth, also D-Ill., that would require the agencies to use polygraph tests during pre-employment screenings and periodic reinvestigations of personnel.

“Our nation’s border and immigration enforcement officers must be held to the same standards of integrity as other federal law enforcement officers,” Durbin told ABC News in a statement. “I’ve introduced a bill to fight corruption and misconduct at CBP and ICE by strengthening the existing polygraph requirement at CBP and initiating a similar requirement at ICE to help ensure that.”

Espaillat told ABC News the episode highlights the need to pass legislation he introduced earlier this year that would require border officers to wear body cameras while on duty.

“Undocumented immigrants and green card holders are terrified,” he said in a statement, “and it is critical that we hold officers accountable and ensure that the civil rights of these individuals are not violated.”

This post originally appeared at ABC News and is posted here with permission.