NEW YORK (AP) — Several bronze plaques commemorating figures from New York City’s rich history have been pried off the buildings they were affixed to this summer, apparently to be sold for scrap metal, part of a disturbing trend that includes the theft of a statue of Jackie Robinson from a park in Kansas.

The losses include a plaque honoring writer Anaïs Nin and one marking the spot where the short-lived rock venue the Fillmore East hosted legendary acts including Jimi Hendrix and the Who.

A third plaque that honored Elizabeth Blackwell, the first woman to earn a medical degree in the United States, was removed from the building where she ran the New York Infirmary for Women and Children but “strangely not stolen.” Instead it was left on the sidewalk, said Andrew Berman, executive director of Village Preservation, which installed the Nin, Fillmore East and Blackwell plaques with the permission of the building owners.

Berman’s group, also known as the Greenwich Village Society for Historic Preservation, has installed two plaques a year for the past dozen years at a cost of $1,250 plus staff time, he said.

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Unlike the monuments to presidents and conquerors that command attention elsewhere in the city, the preservation group’s plaques are meant to honor pioneers who might otherwise be forgotten.

“A disproportionate number of our plaques are women, people of color, LGBTQ people and countercultural sites,” Berman said. “So it’s especially important to try to make this often invisible history visible, and that’s why it’s particularly disheartening that these plaques are being stolen.”

Nin’s stolen plaque on the East 13th Street building where the renowned diarist and novelist ran a printing press said her work there “helped connect her to a larger publisher and a wider audience, eventually inspiring generations of writers and thinkers.”

Blackwell’s plaque noted that the infirmary she opened in 1857 was the first hospital for, staffed by and run by women.

The Fillmore East’s plaque marked the concert hall that promoter Bill Graham opened in 1968, a spot beloved by artists and audiences “for its intimacy, acoustics and psychedelic light shows.”

The New York thefts are not unique. Rising prices for metals have led thieves to target historic markers in other cities including Los Angeles, where plaques at El Pueblo de Los Angeles Historical Monument and Chinatown Central Plaza were stolen last year.

The statue of Robinson, the baseball Hall of Famer who integrated the Major Leagues, was stolen from a park in Wichita in January and replaced this week.

Berman’s group hopes to replace its plaques as well, and is investigating using materials less popular for resale or finding a more secure way to attach the markers.

“We haven’t fully arrived at the solution,” he said.