AVALON, Calif.—Five people were killed when a small plane crashed during takeoff from Santa Catalina Island off the Southern California coast, authorities said Wednesday.

The twin-engine Beechcraft 95 crashed shortly after 8 p.m. Tuesday, just moments after it departed from Catalina Airport near the island city of Avalon, according to the Federal Aviation Administration.

Five people were on board, the FAA said initially. Five adults were found dead at the scene in rugged terrain about a mile west of the airport, the Los Angeles County Sheriff’s Office said.

The crash occurred under “unknown circumstances” during takeoff, and those killed were the pilot and four passengers, the FAA said later in an online incident report. The FAA and National Transportation Safety Board will investigate.

The airfield is known as the Airport in the Sky because of its precarious location at an elevation of 1,602 feet on the island about 25 miles off the coast of Los Angeles. It has a single 3,000-foot runway.

About 4,000 residents live year-round on Santa Catalina Island, where tourists from the mainland are drawn for snorkeling, boating, hiking and strolling the picturesque streets of the oceanfront city of Avalon.