Two persons were slightly injured early yesterday when the ceiling of a cottage at Forest Haven, the District's home for mentally retarded in Laurel, Md., caved in.

Thirty-four mental patients were relocated at the facility after the 3:30 a.m. incident, which occured in the East Wing of Pine Cottage.

According to Clifford Hubbard, acting superintendent of the facility, 17 residents were sleeping in the room when about 50 percent of the ceiling collapsed.

Counselor John Posey, who was in the room at the time assisting a resident, awakened the other residents and told them to get under the beds.

Strips of plaster began falling but much of it landed atop several six-foot high wall lockers in the area.

The cave-in left a 20-by-50 foot hole in the ceiling.

Posey and a resident in his early 40's were taken to Laurel Hospital, where they were treated for minor injuries and later released.

Hubbard said the cause of the collapse is undetermined. An inspection was to be made today. City Administrator Elijah Rodgers has ordered the department of human resources to inspect all nine cottages at the Forest Haven facility.

Hubbard said Pine Cottage is a 54-year-old building. It houses 34 severely to moderately retarded male residents ranging in age from 28 to 60.

The residents in Pine Cottage work on the Forest Haven grounds or in the outside community.