WOODS HOLE, Mass. (AP) – A beluga whale that captured the fancy of boaters and divers with his playful antics last summer apparently died from natural causes, marine mammal researchers said Tuesday.

The whale nicknamed Poco was taken to a laboratory for examination after washing ashore on a mud flat Monday in South Portland.

A preliminary examination showed the whale’s lymph nodes were larger than normal and that tissues surrounding his esophagus were swollen, suggesting he died from an infection, said Dr. Larry Dunn of the Mystic Aquarium.

Tissue samples will be sent away for a conclusive finding, said Dunn, who led a team at the Woods Hole Oceanographic Institution.

The 8- to 9-foot light gray beluga whale made headlines because of his playful nature, rubbing against boats, divers and swimmers. Stories circulated from the islands of Boston Harbor to Maine’s midcoast of Poco pushing around dinghies, squirting water into the faces of giggling children and rolling on his side to get belly rubs .

His many cuts and scars were evidence of dangerous encounters with boat propellers, and marine biologists feared that the whale would meet his demise because of his natural curiosity and playful nature.

But his scars had healed, and there was no evidence of fresh wounds. “I saw nothing internally that suggested human interactions caused his death, and nothing externally that was new,” Dunn said.

Belugas are rarely seen south of the St. Lawrence River in Canada. The whale is endangered and only about 100,000 of them remain.

Whale experts and federal and state officials who had been tracking Poco all summer had hoped he would turn north toward his natural home in the Arctic waters off Canada. He was last sighted Oct. 30 in Maine’s Saco Bay.