HOUSTON — The arrest of a Border Patrol supervisor on allegations that he killed four women calls new attention to the agency’s problems keeping rogue officers off its force as it faces intense pressure to hire thousands more agents.

Juan David Ortiz, who worked in the agency’s Laredo sector, is accused of targeting women believed to be prostitutes in what prosecutors say is the work of a serial killer.

The Border Patrol and prosecutors portrayed Ortiz as an outlier who is not representative of the thousands of employees working for the agency around the country.

“I would hate for this to tarnish the great work that those men and women do,” Border Patrol chief Carla Provost said at a news conference alongside prosecutors and other law enforcement officials.

But Ortiz’s arrest and allegations of violence involving other Border Patrol agents have thrown a spotlight on how the agency vets prospective hires at a time when President Donald Trump wants to bring on 5,000 more agents as part of his crackdown on illegal immigration. Congress has not funded the request.

The Border Patrol has struggled for many years to hire enough agents. Many jobs on the force require living in remote desert towns along the U.S.-Mexico border. Agents must pass a detailed background investigation, and the polygraph exam that’s been required of all applicants since 2012 is a major barrier, with just a 28 percent pass rate between 2013 and 2016.

Rep. Henry Cuellar, a Democrat from Laredo, said Monday that he was weighing whether the agency should consider requiring a psychological examination for all new officers. He said he also spoke to agency leaders Sunday about adding more internal affairs officers. Cuellar is a member of the House subcommittee that reviews the budget for the Customs and Border Protection division of the Department of Homeland Security.

“Is there more to this? Are there other cases throughout the U.S.? It might not be murder, but are there other things that we need to look at?” Cuellar said. “I want to look at the broader aspect and not have a knee-jerk reaction.”