COSTA MESA – A 29-year-old woman was killed when a tree fell onto her car Thursday afternoon, authorities said.

Police received initial reports of a vehicle crashing into a tree, but when officers arrived at the scene, it wasn’t immediately clear how the driver was injured, Costa Mesa police Lt. Mark Manley said.

“It may have been a tree just fell onto the car,” Manley said.

Rescuers about 2 p.m. responded to the intersection of Irvine Avenue and 17th Street, where a 50-foot eucalyptus tree had landed on top of the vehicle occupied by one woman.

A helicopter was initially called to transport the woman to a hospital, authorities said, but was called off when she was pronounced dead at the scene.

Orange County Coroner’s Office officials late Thursday night publicly identified the woman as Haeyoon Miller of Tustin after notifying her family of her death.

Newport resident Pier Warmuth said she was driving a convertible with its windows down westbound on 17th when the tree fell. Warmuth said she didn’t hear or see any collisions and indicated that there wasn’t any wind in the area at the time.

“All of a sudden, there was a weird creaking noise, then everyone was looking around and suddenly there was the tree,” Warmuth said.

A man got out of another vehicle to try to help the woman, Warmuth said, but was unable to reach her.

“There was nothing you could do. The tree was enormous, and it was lying right on the driver’s side,” Warmuth said. “It just happened so quickly. It could have been any of us.”

Authorities denied news reports that the woman may have been communicating after the tree struck the vehicle or that she was re-injured when the tree fell back down as rescue workers attempted to lift it.

Fire crews who arrived minutes after the accident found the woman unconscious and unresponsive, said Fred Seguin, a Costa Mesa fire captain. Paramedics were able to get an IV in one of her arms but were unable to begin rescue efforts because the car had been pushed down.

Using 4-by-4s and airbags, rescuers created a “box” to lift the tree off the vehicle, Seguin said, while a paramedic concentrated on the woman.

Seguin said the tree dropped 3-4 inches when rescuers repositioned the “box,” but he indicated that neither the woman nor a paramedic who was partially in the vehicle was struck.

Rescuers say the woman never regained consciousness while they were on the scene.

“She was not talking to us at all,” Seguin said.

A crane was eventually brought in to remove the tree, which authorities say weighed about 9,000 pounds.

An adjacent tree was removed after a tree expert investigated the area, Seguin said. The other tree was about the same height as the one that fell but about half the diameter, he said.

Both directions of Irvine Boulevard were closed from 17th Street to Mariners Drive as investigators went over the scene and workers removed the tree and the car.

Contact the writer: shernandez@ocregister.com or 949-415-7695