Seventeen juveniles, including two being held on murder charges, escaped from the District's Oak Hill juvenile detention center in Laurel by cutting through a fence yesterday afternoon.

The escape, one of the largest from the institution in recent memory, was part of a plot involving five juveniles and an associate from the outside, who threw a pair of wire cutters into a yard Monday night, officials said.

The cutters were picked up by one of the juveniles sometime yesterday morning and used to cut through the fence.

The five who had formed the plot escaped and 12 others followed them out.

The juveniles apparently also took advantage of an unstaffed security post and the sudden failure of a motion detection system, which allowed them sufficient time to escape, said Robert Little, administrator of the D.C. Youth Services Administration.

Four youths were captured within two miles of the maximum-security prison by late afternoon, and two more had been returned by late last night. The 11 still free were being held on numerous charges, including murder, car theft and drug possession and distribution.

One of the captured youths told authorities that the escape plans were finalized during a telephone call Monday night.

The accomplice on the outside told one of the juveniles that the wire cutters had been tossed into the yard, Little said.

Escapes from Oak Hill and the Annex are not unusual -- 128 youths escaped between January 1988 and January 1989. Oak Hill, designed as a secure facility, is encircled by a high double fence with razor wire. But in the past, as was the case yesterday, the fence has proven easy to cut.

Little said a shortage of guards left one of two security posts briefly unstaffed in the facility's large playground area. Of eight guards normally assigned during the day shift, four were posted yesterday because the rest were transporting prisoners, he said.

That and the failure of the motion detection system -- which should sound the alarm if anyone approaches the fence -- gave the juveniles enough time to cut through the fence.

"The youngsters apparently had done some preplanning, and they spotted a blind spot in security," Little said.

There are 15 openings for guards at Oak Hill, and officials recently were informed they could fill the positions. Little said he is awaiting a list of eligible candidates, which he expects to be delivered shortly by the personnel office.

The escape occurred at 12:40 p.m., when more than 140 juveniles were in a large, fenced recreation area.

One guard sounded the alarm when the last of the 17 escapees was crawling through the hole in the fence, Little said.

The search did not begin in full until the facility was secured and guards conducted a roll call to find out who had escaped, Little said. Under established cooperative arrangements, Maryland State Police, U.S. Park Police and law enforcement agencies in Anne Arundel County were told of the escape.

Oak Hill is minutes from the Baltimore-Washington Parkway and inside wooded federal parkland, which makes it difficult to conduct searches. Little said about two-thirds of escapees are caught, most within six hours.

Officials were still gathering information on the juveniles who were missing. Some of them are recent arrivals into the system; others have been there for a year or longer.

Little said the two being held for homicides are believed to be awaiting trial. Details of the cases were not available because officials had not had time to review the files, he said.