ORLANDO, Fla. -

The killer whale responsible for a trainer's death last year is undergoing medical treatment.

SeaWorld Orlando officials said Thursday that Tilikum has been moved to a medical pool that allows trainers and veterinary staff to monitor his progress.

The SeaWorld officials didn't specify what is ailing the killer whale but noted that he had shown signs of improvement on Thursday.

Trainer Dawn Brancheau died in February 2010 when Tilikum grabbed her and dragged her underwater violently.

SeaWorld currently is appealing a $75,000 fine for three federal citations it received following Brancheau's death.