The Los Angeles County Department of Medical Examiner said the deceased included Gonzalo Lubel, 34; Harris Ali, 33; Ali Safai, 73; and Margaret Fenner, 55.
The twin-engine Beechcraft 95 went down shortly after 8 p.m. Tuesday, just moments after it departed from Catalina Airport near the island city of Avalon.
Five people were on board, the FAA said. Five adults were found dead at the scene in steep, rugged terrain about a mile west of the airport, the Los Angeles County Sheriff's Department said.
The sheriff's Avalon Station received a 911 SOS emergency notification from a cellular device stating that its user may have been involved in a collision with possible injuries, authorities said.
"It gives coordinates to a location, so it's not necessarily like a street name or a landmark," said Deputy Jacob Sivley. "It's just a coordinates on a map so deputies had to saturate the area and try to locate where this SOS notification was coming from."
The device-provided GPS coordinates enabled rescuers to locate the wreckage and the bodies of the five people onboard.
5 killed after twin-engine plane crashes on Catalina Island; investigation underway
It's believed that the aircraft started off at Santa Monica Airport, traveled to the island and departed again before it crashed.
When deputies arrived at the scene, the plane appeared to be mostly intact, officials said.
It remains unclear what caused the crash, but the island's airport presents its own set of challenges for pilots, according to AIR7's Scott Reiff.
The airport is primarily used for general aviation aircraft, including single-engine airplanes and is known as the Airport in the Sky because of its location at an elevation of 1,602 feet. It has a single, 3,000-foot runway.
"I've landed there multiple times in an airplane. It's tricky," Reiff said. "You approach... basically over a cliff and when you come into the airport, as you start to descend, you can't see the end. There's a hump in the middle, so it's deceiving exactly how long the runway is."
Deadly plane crash sheds light on challenges pilots face at Catalina Island's airport
The specific aircraft that crashed is only designed to hold four people, but there were five on board at the time. Investigators will determine if that was a factor.
"Our aero bureau is going to be responding with the Los Angeles County medical examiner with our emergency services detail to work in their duties on that rough terrain as much as they can," Sivley said Wedneday.
Along with the Sheriff's Department, the crash was being investigated by the Federal Aviation Administration and National Transportation Safety Board.
The Associated Press contributed to this report.