Federal officials are investigating reports that the head veterinarian at ZooTampa accidentally killed at least two manatees with shoddy medical care.

They are also asking questions about "credible reports" that Dr. Ray Ball, head veterinarian at what was formerly known as the Lowry Park Zoo, performed improper field amputations on wild manatees.

Until the investigation is over, the U.S. Fish and Wildlife Service said in an Oct. 22 letter to the zoo, Ball must "cease all activities involving manatees." The zoo's own permit for treating and exhibiting the marine mammals may be in jeopardy, the letter said.

"Because of the nature of the questions posed, Dr. Ball will be on paid administrative leave while we review veterinary care procedures and gather the information needed," the zoo's CEO, Joe Couceiro, said in a statement issued late Thursday.

These complaints should come as no surprise to the zoo's management, according to a zoo employee who previously worked with Ball in caring for manatees.

"I and many others have had issues with his style of medical care and extreme negative results that have come with it," said Jennifer Galbraith, who resigned from the zoo staff this week after 15 years. "We have over the last eight years documented and presented multiple times this information to the zoo management. At no point has Dr. Ball been held accountable for these actions."

She said she is far from the first person to resign in protest over Ball's treatment of animals.

But Couceiro said that the zoo's administrators "always promptly and appropriately address all questions about animal care protocols and procedures."

The federal agency's questions, and Ball's suspension, come at a particularly awkward time for the zoo, which has been caring for injured and ill manatees since 1991. Its David A. Straz, Jr. Manatee Critical Care Center is about to reopen after being shut down for a year for a taxpayer-funded $3 million upgrade to the manatee tank's water filtration system.

READ MORE: Lowry Park Zoo changes name, will add water ride and increase wildlife capacity.

As a statewide Red Tide algae crisis has killed nearly 200 manatees this year, the need for the zoo's manatee care facility is critical.

The zoo did not make Ball available for comment, but zoo senior vice president Larry Killmar said what's going on is less an investigation and more in the nature of a federal inquiry. He was unable to explain the difference.

Killmar, who also serves as zoo director, denied that Galbraith or any other employee had ever filed a prior complaint about Ball's medical treatment of animals.

READ MORE: Clues to combating Red Tide are found in mounting manatee carcasses.

He said he could not comment specifically on the "credible reports" cited in the letter from the Fish and Wildlife Service, except to say that the zoo is now in the process of assembling a panel of experts on veterinary care and manatees to review the complaints.

"We're in the process of putting that group together now," Killmar said.

The letter points to four aspects of Ball's medical treatment that raised questions.

The first involves a treatment called "chest taps." When manatees are hit by boats, their ribs can break and puncture a lung so they are unable to submerge. A chest tap involves sticking a needle into the manatee's chest to remove the air and determine the size of the puncture. But the needle can go in too deep and puncture the lung again.

"After chest taps were performed by Dr. Ball," the federal agency's letter said, "two manatees died, and the necropsy reports showed perforations in the lungs from chest taps."

The second item involves the rescue of wild manatees that had become entangled in fishing line.

"On more than one occasion," the letter states, "Dr. Ball performed in-field amputations of manatees' flippers, at times without treatment for infection and pain, and at times releasing the manatees with exposed bones."

The third point looked at drugs Ball used on injured or ailing manatees.

"On more than one occasion," the letter says, "experimental drugs and/or experimental methods of administering drugs were used." He would give combinations of drugs "for which he did not have or did not use equipment needed for the procedure."

The final point, the letter said, concerned "the feeding of hay to young/growing manatees or animals that are physically compromised." Hay offers no nutritional value to manatees, which eat aquatic plants. However, it does tend to be cheaper.

Galbraith said the animals that were fed hay were not housed at the zoo but at the Ellie Schiller Homosassa Springs Wildlife State Park, which was holding manatees in need of rehabilitation while the zoo's hospital was closed. They were young manatees that had been injured or fallen ill, and thus needed increased feeding of lettuce and other nutritional items while they recover.

However, she said, Ball has told the zoo staff he thinks manatees in captivity are fed too much, and should get hay instead.

Galbraith said one young manatee at the Homosassa park, a former roadside attraction, was injured in a freak accident when it got into the cage of the famous hippo Lucifer, 58. The hippo was declared an honorary citizen of the state by then-Governor Lawton Chiles in 1991.

Ball said the orphaned manatee had suffered only a few scrapes and two months later he cleared it for release back into the wild. However, the manatee still had open, bleeding wounds, she said.

However, the manatee still had open, bleeding wounds that another veterinarian said appeared to be the result of being bitten by Lucifer. When the young manatee's condition was reported to the authorities, the release was canceled. It was transferred to SeaWorld for further care. That case led to the federal questions about Ball.

"That was pretty much the powder keg that blew the lid off," she said.

Until the complaints about Ball have been cleared up, Killmar said, all manatee treatment will be handled by associate veterinarian Lauren Smith, who has worked there since 2015.

Ball has been licensed as a Florida veterinarian since 1992, and his current license does not expire until 2020. As of Wednesday, state licensing officials said they have received no complaints about Ball.

He was previously employed by Busch Gardens in Tampa starting in 2006, and moved over to Lowry Park in 2010, where he replaced veterinarian David Murphy.

Murphy said this week that he had never been subjected to a similar inquiry or investigation like the one now aimed at Ball.

"I never received a letter from the Fish and Wildlife Service telling me I couldn't treat manatees," he said. "I got an award from the Fish and Wildlife Service for treating manatees."

Murphy said he could not comment on the investigation but he acknowledged that the timing could not be worse for the zoo.

"It certainly puts them in a ticklish situation," he said. "I guess they have some explaining to do."

Senior news researcher Caryn Baird contributed to this story. Contact Craig Pittman at craig@tampabay.com. Follow @craigtimes.