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The world’s oldest captive manatee died in a tragic accident just one day after his 69th birthday party, the South Florida Museum announced Sunday.

An investigation has been launched into the death of Snooty, who was listed in the Guinness World Record 2017 Edition as the World’s Oldest Manatee in Captivity.

“The South Florida Museum is deeply saddened to share the news that our beloved Snooty has died,” the museum said in a statement. “Snooty’s death was a heartbreaking accident and the circumstances are being investigated so we can be sure we know the full details of what happened.”

Three other manatees at the museum’s Parker Manatee Aquarium were all reported to be in good condition.

“We know that our community and Snooty fans around the world share our grief,” the statement said.

The museum, which happens to be in Manatee County, declined to comment to NBC News on the exact cause of Snooty’s death.

Museum staff said Snooty was found in an underwater area only used to access plumbing for the exhibit life support system, according to the museum.

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An access panel door that is typically bolted shut had been knocked loose and Snooty was able to enter, museum officials said.

Jeff Rodgers, the Provost and COO of the South Florida Museum, described the area the manatees were able to access as a long hallway, in which Snooty, who weighed 1,300 pounds, was unable to turn around.

"The manatees had access to get into this tight area. The young manatees were able to get in and out of that, and it appears that Snooty was able to get into the area, but he was not able to extract himself from that situation," Rodgers during a press conference Sunday. "It took us some time to figure out exactly how we were going to deal with that situation, but when we did finally get to Snooty, he was no longer alive."

Snooty was described as am intelligent, social manatee, who had the staff of the South Florida Museum under his flipper.

In this photo taken Wednesday, July 17, 2013, Snooty the manatee lifts his snout out of the water at the South Florida Museum in Bradenton, Florida. Tamara Lush / AP file

Related: Is Sound the Secret for Saving the Manatees?

"He's just entertaining and calming at the same time," Marilyn Margold, director of living collections at South Florida Museum, told Guinness World Records in 2016

Snooty first arrived at the South Florida Muesum in Bradenton, Florida, in 1949, at just 11 months old.

Margold said Snooty’s longevity was a testament to how long the species can live when cared for properly.

Snooty was a one-of-a-kind community mascot who brought joy to everyone who saw him. He will be missed. https://t.co/GQq9rbcIt1 — Manatee County Gvt (@ManateeGov) July 23, 2017

Snooty was Bradenton's gem. We are saddened to hear this news. He provided joy to our students for nearly 7 decades. RIP Snooty. https://t.co/iSqHuV765U — Manatee Schools (@Manateeschools) July 23, 2017

Rumors swirled around Southwest Florida that Snooty died years ago and has since been replaced by different manatees, according to the Associated Press, but Margold said Snooty's scars, distinct tail, and warm personality would have been hard to recreate.

In a tweet, Manatee County Schools said the beloved marine mammal would be sorely missed.

"Snooty was Bradenton's gem. We are saddened to hear this news. He provided joy to our students for nearly 7 decades. RIP Snooty," the tweet said.

Manatee County Government also tweeted about Snooty's passing.

"Snooty was a one-of-a-kind community mascot who brought joy to everyone who saw him," it said. "He will be missed."

Most wild manatees die before the age of 10, and can be victims of alage blooms, fishing debris and boat strikes. However, earlier this year, manatees were taken off the endangered species list and upgraded to "threatened."

The oldest living wild manatee made it to 59 years old, with the second oldest reaching 48 years, according to the Florida Fish and Wildlife Conservation Commission, LiveScience reported.

"Taken proper care of, paying attention to their habitats, those things can help with their longevity. They are hearty animals overall," Margold said.