Over the past few days, thousands of federal prisoners have been leaving confinement early and returning to their communities — the result of changes to sentencing guidelines for drug-related crimes.

And who will be monitoring those former inmates?

In some ways, the buck stops with Matthew Rowland. He's the chief of the probation and pretrial services office at the Administrative Office of the U.S. Courts.

Rowland worked as a federal probation officer in his native New York for 15 years. Now he's responsible for a nationwide team that supervises about 225,000 people accused or convicted of federal crimes every year.

Rowland told NPR he's been able to hire a net 150 new officers to help deal with the big release of drug offenders. The officers started working with many of those criminals a year ago, even before they left prison.

"The officer is required to interact with them not only in the office but go out into the community and see where they're living, see who they're hanging around with, see the level of family support they have and then take that information into account in developing a supervision plan that tries to produce the best possible result," Rowland said.

Rowland said his probation officers, about half of whom have master's degrees or doctorates, are familiar with occupational hazards, like this one: "We always joke that nobody gets lied to more than a good probation officer."

To deal with deception, federal probation officers enlist people in the community to make sure former prisoners stay straight, reaching out to clergy, police and relatives to flag the kinds of interactions that should be out of bounds.

"Sometimes a mother is much more powerful than a probation officer ever could be and they have a greater impact and we acknowledge that," he added.

Federal judges have signed off on each of the recent prisoner releases. But assurances from judges and probation officers aren't enough for some in law enforcement or on Capitol Hill.

Alabama Republican Sen. Jeff Sessions expressed his worries about the prisoner release last month.

"Put bluntly, when we release large numbers of criminals early, we know that a substantial number of those individuals will commit murders, rapes, assaults, robberies and other violent crimes that would have been prevented had they remained in prison," Sessions said.

Rowland acknowledged the system isn't perfect. He said about 2 in 10 criminals under federal supervision are arrested again on felony charges within three years. But he said many of the drug offenders released recently would have gotten out anyway, eventually.

"Some of these people are not going to succeed," Rowland said. "And they wouldn't have succeeded whenever they were released. And it's our job to minimize the harm they are going to create."

Copyright 2016 NPR. To see more, visit http://www.npr.org/.