PLYMOUTH, Mass. (AP) – Divers searched a pond Sunday for the bodies of a 21-year-old woman and 16-year-old boy who fell out of a canoe in near-freezing weather during a late-night outing after a birthday party.

Two other canoeists who were in the same boat when it overturned were pulled out of Great South Pond just after midnight, and were recovering in hospitals.

A short time after the rescue, authorities recovered the canoe along with a sneaker and a baseball cap floating near shore, Plymouth Fire Chief Jim Pierson said.

An initial four-hour search for the missing canoeists shifted from a rescue attempt to a recovery operation Sunday morning at 8 a.m. as arriving divers looked for bodies in the chilly water and a helicopter circled overhead. About 15 divers took part, but no additional signs of the missing canoeists had been found as of noon, Pierson said.

The pond stretches more than a half-mile across, and is as deep as 50 feet in some spots.

Authorities did not immediately release the names of the missing canoeists or the two male survivors. The missing 21-year-old woman was believed to have been the girlfriend of one of the survivors, Pierson said.

Relatives of the survivors told investigators the group had attended a birthday party Saturday night for a 78-year-old grandmother of one of the four, Pierson said. The party was in Braintree, about 35 miles northwest of Plymouth.

Authorities were unsure what led the group to go canoeing late at night in temperatures in the 30s, apparently without life jackets or flotation devices, Pierson said.

“My sense is that they felt it was a way to complete the evening,” he said.

The green canoe apparently capsized, but investigators were unsure why, Pierson said. An inspection revealed no obvious problems with the boat.

Rescue workers were called to the scene at 11:42 p.m. after neighbors reported they heard screaming. The pond is surrounded by summer cottages on the outskirts of Plymouth near Myles Standish State Forest, about 45 miles southeast of Boston.

One man who was pulled from the water was taken by medical helicopter to Massachusetts General Hospital in Boston. The other was being treated at Jordan Hospital in Plymouth.

Both were being treated for symptoms of hypothermia, Pierson said. Their conditions were not released.