A Maine medical examiner has been unable to determine the cause of pop artist Robert Indiana's death, but a spokesman says the death was not suspicious.

A spokesman told The Associated Press on Friday that the death of the artist known for his iconic LOVE sculptures was likely cardiac-related, but the official cause and manner of death is "undetermined."

Indiana died May 19 at age 89 at his home on Vinalhaven Island off the coast of Maine. His attorney said he died from respiratory failure.

An FBI agent investigating possible art fraud requested the autopsy. A federal lawsuit accuses two men of insinuating themselves into Indiana's life and taking advantage of him in the final years of his life.

Philly's LOVE sculpture, which gave John F. Kennedy Plaza its "LOVE Park" nickname after its installation in the 1970s, has been the backdrop to countless engagement and Valentine's Day photos. Though, similar installations can be found across the world, including in the artist's home state of Indiana as well as in Israel. The design was also a popular U.S. stamp.

LOVE Park recently reopened after a two-year-long, $26 million redesign, while the sculpture itself underwent its own facelift and was restored to its original colors of red, green and purple.

"The piece has come to symbolize the city because it resonates with Philadelphia's foundation," Barbara Haskell, a curator at the Whitney Museum of American Art, said after Indiana's death. "LOVE has this very positive, ebullient, and euphoric sense about it, but it also touches on the ideas of pain and disappointment. Its power is in that it encompasses both things."