Two young sisters who had been missing from their Colesville home for several hours were pulled unconscious late last night from a nearby ice-covered pond, authorities said.

The girls, identified by police as Michelle Luna, 11, and her sister Rachel, 9, were flown by helicopter early this morning to Children's Hospital in the District, where they were listed in critical and unstable condition.

The girls were rescued about midnight from a pond in Valley Mill Park, which is off East Randolph Road and less than half a mile from their home on Serpentine Way in Montgomery County, authorities said.

They were found an hour after searchers spotted a hole in the ice covering the water. The girls were in water six to eight feet deep, according to a spokesman for the Maryland National Capital Park Police.

The police spokesman said there was an unconfirmed report that the girls may have telephoned their home about 6 p.m. and left a recorded message.

The girls' parents, who were not immediately identified, called police about 8:30 p.m. to report the children missing, the spokesman said.

The spokesman said a neighbor told police that the girls had been playing in the park in the afternoon.

After seeing the hole in the ice about 10 p.m., he said, searchers called for the Montgomery County Fire and Rescue Department's search and rescue team.

The thickness of the ice at the point where the girls were found could not be learned immediately, but Park Police Sgt. Timothy Boyle indicated it was solid enough in spots to resist rescuers' efforts to break it.

After the girls were pulled from the water, paramedics began administering first aid.