The Montgomery County County Council authorized $615,000 yesterday for 17 guards and other improvements at the county jail after officials said drug crackdowns and other law enforcement programs had contributed to an increase of nearly 15 percent in the inmate population.

Corrections Director Calvin Lightfoot said the jail held 516 prisoners yesterday, up from about 450 in September. The jail's official capacity is 450, but Lightfoot said the additional inmates have been accommodated by putting second bunks in some cells.

Lightfoot said increased police staffing in the last year had resulted in more arrests. He also cited the police department's "jump-out squad," which has cracked down on street drug sales since its formation last fall, and the department's repeat-offenders unit, which was started last July to target suspects wanted on outstanding warrants.

"When you increase the number of law enforcement officers, and they make more arrests, this is going to happen," said Lightfoot, who could not say how many inmates had entered the jail as a result of the jump-out and repeat-offenders programs.

County Executive Sidney Kramer approved the new staffing in December, after the jail population reached a peak of 550 in November, in what jail officials said was a seasonal increase. But the council had not yet approved funding for the additional guards.

Lightfoot said the new officers were hired in February and there are 118 correctional officers at the jail, which is located at 1307 Seven Locks Rd.

In a memo to the council, legislative analyst Jennifer Andrews told the council that corrections officials had failed to properly foresee the effects of the increase in arrests. "The impact on the jail population of these factors should have been planned for," she wrote.

Lightfoot said corrections officials had been aware of the jump-out squad and repeat-offenders programs, but had to wait to see the impact on jail population before they could request more staffing. "These things happen," he said. "Society changes its attitudes and says we want to arrest more people for drugs. It's all for the right reasons."

As part of its action, the council authorized $152,770 in overtime payments made before the new guards were hired. Under questioning from council member Michael Subin, who voiced worry that too many county departments were using overtime to compensate for inadequate staffing, Lightfoot said overtime costs are "back on track."

The council also approved $19,000 for a metal detector at the jail's visitors entrance and a new window in the visitors area. Those improvements were made after an escape attempt in September in which an inmate's friend tried to cut through a window in the visiting area with a blowtorch.