A seal rescued from a Middletown beach in February has died, according to the Marine Mammal Stranding Center in Monmouth County.

Staff say the seal had just completed prerelease vet exams and was nearing its return to the wild.

It became extremely lethargic late Sunday night, and its health rapidly declined.

"MMSC’s staff and veterinarian worked throughout the day to stabilize the Harp seal, but despite their best efforts, the seal’s condition continued to decline rapidly throughout the day," officials wrote in a Facebook post.

The seal was euthanized Wednesday afternoon.

"This loss has been particularly painful for our team as this patient had come so far in the month that he was with us, and it seemed that his return to the wild was on the horizon," officials wrote.

The center plans a full necropsy to determine the cause of death.