Thirteen youths fled the District of Columbia's Oak Hill juvenile detention center in Laurel last night in what appeared to be the largest escape ever from the facility.

The youths, aged 16 to 18, escaped about 8:30 p.m. by slipping out of their cottage through an unlocked door, then tunneling under one fence and climbing over another, officials said. As of 2:30 a.m. today, 11 of the youths were still at large.

According to Rayford Myers, the institution's superintendent, all 13 had been committed to Oak Hill by the District's juvenile court on a variety of charges, almost all misdemeanors.

No injuries were reported in connection with the escape from the center, which is located near the Baltimore-Washington Parkway and Fort Meade.

The two recaptured youths were taken into custody by Maryland State Police troopers shortly after 2 a.m. today after they were spotted walking along the parkway about 4 miles south of the detention center. A third youth walking with the pair fled into a nearby wood. The two were clad in Oak Hill-issue blue jeans and gray sweatshirts, as were the other 11 youths when last seen at the facility.

Oak Hill and the city's other two youth detention facilities, Cedar Knoll -- also in Laurel -- and the Juvenile Receiving Home in Northeast Washington, have been plagued by escapes over the years.

Last year, nine youths escaped from Oak Hill by prying open a fence with wirecutters. That was the largest number to escape from the institution since 10 youths broke out in 1968, the year it opened.

The facility houses 150 youths in four cottages, each divided into two sections.

All the youths who fled last night came from the same section of one of the cottages.

Myers said one of the section's two security guards, who were not armed, was taking his lunch break at the time of the escape.

The other guard, who was watching television with some of the youths in the cottage, was told by some of the escapees that they were going to the bathroom, which is down a hall and out of sight of the television area, Myers said.

Instead, he said, the youths left the cottage and dug under the institution's inner fence, which is 16 feet high and topped with concertina wire. Myers said a shovel was later found nearby.

After digging under the inner fence, the youths climbed over an outer fence, which is 10 feet high and topped with barbed wire, Myers said.

He said the incident will be investigated.