The wreckage of a D.C. police helicopter that crashed near the Jefferson Memorial Saturday, injuring two officers, was taken to a hangar at National Airport to be examined by federal authorities yesterday to determine what caused the crash.

The pilot of the helicopter, Joseph M. Ruth, 32, was treated at the Washington Hospital Center for minor injuries and released yesterday. Officer Kenneth E. Boone, 33, who was acting as an observer in the two-seat Bell 47G-4 craft, was treated for a sprained right leg at George Washington Hospital and released.

Ira Furman, a spokesman for the National Transportation Safety Board, said the helicopter was being examined at a hangar at National Airport yesterday.

"We've had an investigator out there through the night looking for an effective way to test the engine, but we'll also want to talk to the two people on board to get a better idea of what happened. Right now we don't have any factual determination on if there was any mechanical failure."

Police officials said the helicopter had been on a routine patrol and was returning to the police hangar at National Airport when the pilot radioed police communications to report "mechanical difficulties" at about 8:40 p.m.

The helicopter lost radio contact moments before witnesses reported seeing it strike the upper limbs of a large tree and fall about 50 feet before crashing in a grassy area near the approaches to the 14th Street bridge.