Two dead, two hospitalised and one still missing after medical helicopter crash off California's Catalina Island

A medical helicopter transporting a patient to the mainland for further treatment crashed into the water off Catalina Island near Los Angeles on Wednesday night. Authorities said two people were killed in the crash, while two others were hospitalised.

Rescue teams, including the Coast Guard, firefighters and divers from the Los Angeles County Sheriff's Department, searched through the night and into Thursday for a fifth person who was aboard the aircraft when it went down.

The cause of the crash has not yet been determined. Coast Guard Captain Stacey Crecy said the helicopter crashed shortly after takeoff, hitting the water a short distance from the island, while transporting a patient off the island for additional care on the mainland.

Relatives told US media the missing woman was being flown for treatment after suffering an allergic reaction, and that her 20-year-old son had accompanied her to help with translation.

At an afternoon press conference, Sheriff Robert Luna said authorities had not yet released the victims' names, but confirmed the two who died were the male pilot and a female nurse. Another medic and a fourth man were hospitalised.

The helicopter's operator, REACH Air Medical Services, based in Sacramento, confirmed two of its crew members died and a third was recovering in hospital. The company declined to share further details, saying its focus in the coming days would be on supporting its staff and their families.

A memorial service was held on the island in honour of the victims. The crash is the third involving a helicopter in California in recent weeks — it came 11 days after a firefighting helicopter crash killed two pilots in Yosemite National Park, and two weeks after a news helicopter crash in Los Angeles killed two people.

First responders were called to the scene shortly before 8pm local time on Wednesday and pulled four people from the water. Two were pronounced dead at the scene, while two in stable condition were taken to hospitals on the mainland. The National Transportation Safety Board is investigating and has identified the aircraft as a Eurocopter EC-135-P2. The helicopter is submerged in around 70 metres of water and is expected to be recovered following an on-site inspection.