MONTGOMERY COUNTY corrections director Arthur M. Wallenstein says the mistaken releases of five inmates from the Rockville detention center last year were regrettable but not cause for alarm. He notes that every inmate was recaptured within a few days and that none was believed to have committed crimes while at large; besides, 22,000 inmates pass through the jail and an adjacent processing center each year. But people living nearby may not regard even one incident all that lightly. They should at least be informed of such releases, as they have not been. The department never notified the public, County Executive Douglas M. Duncan or anyone on the County Council. The incidents were noted in corrections records obtained by this newspaper. "It came as a complete surprise to me," Mr. Duncan said. "It's not acceptable that I wasn't told, and it's certainly not acceptable that people were being released prematurely."

In at least one case, Mr. Wallenstein must have had cause for alarm. When he learned that a repeat offender awaiting trial on theft and burglary charges had been mistakenly released, he sent an urgent e-mail to top jail staffers, calling it "a bona fide public safety emergency" and stating that "all else comes second until we have him."

Montgomery's center is no sieve, but five incidents in one year are reason enough for an investigation of operations there. The foul-ups resulted from sloppy work: mistakes in paperwork, miscalculated sentences and the release of one man in place of his cousin. With a new detention center about to open in Clarksburg -- where neighbors will be looking for reassurances that all is under tight control -- Mr. Duncan and the council must act to ensure vigilance.