PALATKA, Fla. (AP) — Two Mayo Clinic employees and a pilot flying to a University of Florida hospital to retrieve a heart for a transplant were killed when their helicopter crashed Monday in north Florida, officials said.

The helicopter departed the Jacksonville hospital around 5:45 a.m. but never arrived in Gainesville, about 60 miles southwest, said Kathy Barbour, a spokeswoman for the Mayo Clinic.

The employees' names were not released because relatives hadn't been notified.

"Mayo is working internally to support the family and employees of those lost in this most unfortunate tragedy," Barbour said.

The employees were on their way to pick up a heart for a transplant in Jacksonville, Mayo Clinic spokesman Carl Oestreich told The Associated Press.

The helicopter crashed about 12 miles northeast of Palatka, said Federal Aviation Administration spokeswoman Kathleen Bergen.

Clay County Sheriff's Office dispatcher Myron White confirmed that three people died in the crash, but no additional information was immediately available from the crash site. Palatka is about 40 miles east of Gainesville.

The National Transportation Safety Board also was investigating.

FAA records show the Bell 206 helicopter is owned by SK Jets. An employee who declined to give her name said the St. Augustine company had no immediate information.

Gary Robb, a Kansas City aviation attorney specializing in helicopter safety, said SK is known as a careful and safe operator in the industry.

The Bell 206 helicopter is a small, lightweight aircraft that has low weight and speed capabilities, and it's primarily used by traffic reporters or police departments, Robb said.

"It's not usually used in donor flights," he said.

"If you're on a mission where time is sensitive, why use an engine that is low performance?" Robb said, adding that the helicopter has a cramped cabin.

An NTSB investigator will scour the crash site for clues and look into the pilot's experience and any factors that might have impaired the pilot, any environmental factors such as birds or low visibility that may have contributed to the crash, and any mechanical problems with the helicopter, he said.

The Bell 206 helicopter usually has an older engine no longer installed in new helicopters, Robb said.

"We've seen a number of instances where that engine simply failed," Robb said.

The crash and others like it illustrate that just transporting the organs for transplants can be a delicate endeavor.

In 1990, a surgeon and an assistant flying to pick up a donor heart for a patient were killed in a plane crash in New Mexico. And in 2007, a twin-engine plane carrying a team of surgeons and technicians — along with a set of lungs on ice being brought to a patient already prepped for surgery — crashed into the choppy waters of Lake Michigan.

Doctors ultimately got another set of donor lungs that were transplanted into the patient.

Copyright 2011 The Associated Press.