By Michael Fleeman

LOS ANGELES (Reuters) - A 14-year-old boy reported missing last week has been found dead in South Lake Tahoe, apparently killed by a 50-foot tree knocked down during a storm that struck California late last week, police said on Monday.

Dejon Smith, a freshman at South Lake Tahoe High School, was reported missing on Thursday after he left school and never returned home. A witness saw him in a wooded area that evening, but a police search failed to find him.

His body was found by a resident on Saturday about half a mile from where he was last seen, authorities said. South Lake Tahoe police said an initial investigation suggested he was hit by the large tree during the severe storm that pummeled the Pacific Northwest and California on the night he disappeared.

The teenager appears to be the third person killed by falling trees during the storm, which also saw flash floods and mudslides that prompted the evacuation of hundreds of homes and disrupted passenger rail service along the coast.

In southern Oregon a homeless man camping with his 18-year-old son died on Thursday when a tree toppled onto their tent, and Portland police said a tree fell on a car that then swerved into another tree, killing a boy who was a passenger.

The severe weather was spawned by a storm system dubbed a "pineapple express," a large low-pressure area that siphoned vast amounts of moisture from the tropical Pacific near the Hawaiian islands and dumped it on the West Coast as it moved over land, the National Weather Service said.

But it is expected to provide little relief from the multiyear drought that has forced sharp cutbacks in irrigation supplies to farmers and prompted conservation measures across California.

(Reporting by Michael Fleeman; Editing by Daniel Wallis and Eric Beech)