Federal judges in Massachusetts have begun ordering the release of prisoners convicted of crack cocaine offenses, responding to a government decision to retroactively reduce the harsh penalties for using and selling that particular form of the drug. Up to 30 could be affected.

Since Feb. 6, judges have reduced by 15 to 33 months the sentences of at least three Massachusetts inmates imprisoned for crack offenses. As a result, two who have already exceeded the shortened sentences will be freed March 3, the first day prisoners are eligible for lightened punishments for crack-related crimes. A third is expected to be released in June.

In one case, US District Judge William G. Young criticized the US Sentencing Commission for failing to implement the new sentencing structure right away when it voted on Dec. 11 to make the lessened penalties retroactive for some 19,500 federal prisoners nationwide.

"The failure of the Commission immediately to implement its solution to the 'fundamental unfairness' in the way crack cocaine offenders were treated under the previous version of the guidelines . . . virtually guarantees that some defendants . . . will spend more time in prison than they should have," Young wrote Tuesday.

Young said one convicted crack dealer, Carlos Gagot, would be finished with his sentence as a result of a 33-month reduction at the request of the defense and government. But the judge said he was pow erless to free Gagot immediately. Still, Gagot "ought not spend one more day in prison than necessary" and should be freed March 3, Young wrote.

Miriam Conrad - head of the federal public defender agency in Boston, which represented the three defendants whose releases have been ordered - said her office has come up with a list of at least 27 other inmates who may be eligible for sentence reductions.

"I'm getting letters from prisoners on a daily basis," she said.

An analysis by the US Sentencing Commission, which voted unanimously Dec. 11 to lighten punishments retroactively for some crack offenses, said 91 prisoners convicted in federal courts in Massachusetts will be eligible through 2012 to seek reductions of sentences imposed for selling or possessing crack. But Conrad said she believes the number could be much higher than 91.

Christina DiIorio-Sterling - a spokeswoman for US Attorney Michael J. Sullivan, whose office agreed to all three sentence reductions - said many factors will determine how prosecutors treat such applications.

"In general, there will be some offenders for whom early release may be appropriate, given the reduction in sentencing as mandated by the changes in the guidelines," she said.

Advocates for such offenders were buoyed by the first reductions in sentences to take place as a result of the government's effort to reduce the stark disparity between punishments for crimes involving crack cocaine and those involving cocaine powder.