Washington (CNN) -- Federal prison officials fail to properly keep track of thousands of inmates who are granted unescorted furloughs when they are temporarily released, an investigation by the Justice Department's inspector general has concluded.
More than 90,000 federal inmates were allowed to leave institutions unescorted in the past three years, often for medical reasons.
Currently, the federal Bureau of Prisons operates the furlough program using manual processes. The investigation found the prison system does not have accessible or accurate data on inmate escapes while on furlough, nor on crimes committed by furloughed inmates.
The report sharply criticizes the Bureau of Prisons for failing to implement proposed policy improvements drafted seven years ago. Among the policy changes still awaiting implementation is a requirement to notify crime victims and witnesses when a prisoner is being temporarily released.
Inspector General Glenn Fine's investigation said the Bureau of Prisons blames the delay in implementing the policy changes on negotiations with the prison union. The bureau estimates it will take another seven years before the policies can be put in place because of the cumbersome negotiating process.
Fine said it would be "excessive and unacceptable" to delay until 2017 improvements to the furlough policy that would enhance victims' rights.
About 13 percent of the prison population qualifies for furloughs each year. Furloughs are authorized absences by an inmate not under the escort of a Bureau of Prisons staff member.
The prison system has two types of furloughs: transfer and nontransfer. The report says there is a lesser problem in nontransfer furloughs, in which a prisoner returns to the same institution. The absences are for short-term medical treatment, to strengthen family ties or to allow participation in approved activities.
But with transfer furloughs -- in which prisoners are being moved for longer-term treatment at a medical facility or a halfway house -- the documentation tends to fall apart, the report says.