All last summer it was a colorful and Instagram-approved piece of undulating art dangling over the Rose Kennedy Greenway.

But now Janet Echelman’s aerial sculpture “As If It Were Already Here” is at the center of questions about how the taxpayer-supported Greenway Conservancy spends money.

The sculpture, which soared hundreds of feet over Boston last year, cost more than $1.7 million, three times an original cost estimate of $500,000. The overrun was the centerpiece of a scathing report authored by anonymous tipsters calling themselves the “Greenway Whistleblowers,” which was first reported by the Boston Herald.

The Herald reported that the tipsters claim to be “a group of past and present volunteers and staff members.”

In response to the reports allegations of financial misconduct, the Greenway Conservancy has since said it will conduct an internal investigation.

Bud Ris, a member of the Greenway’s board, will lead the investigation, which conservancy officials described as a move that follows its policy whenever similar allegations are made.

The group has confirmed that the $1.77 million figure cited in the report is accurate.

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The  sculpture was funded with donor and grant money and not with public funds, said Michael Nichols, the Conservancy’s chief of staff, in an interview with the Globe.

The Greenway was open about the fact that costs could go up, he said. Erecting and taking down the sculpture was a big affair involving a crane-wielding crews to attach and remove fixtures on the sides of buildings. 

The installation and decommissioning costs, he said, were a “known unknown.”

According to Jesse Brackenbury, the conservancy has a balanced budget. He also said the report’s accusations of mismanagement “depart significantly from reality,” according to the Globe.

“Project costs went up, revenues went up, but we ran a balanced budget, and we delivered the most transformational public art project that Boston has seen,” Brackenbury told the Globe. “Nobody’s asking the [Museum of Fine Arts] what it costs to put on a show, and we’re not putting on a show behind a gate that people have to pay for. We’re putting on public art for the public — and we’re doing it with entirely private dollars.”

The nonprofit conservancy grooms, gardens, maintains and runs programming for the Greenway using a blend of public money and funds from donations, endowment income and upscale fundraising events.

The controversy surrounding the report and the Echelman sculpture’s larger-than-life price tag could spell new trouble for the conservancy, whose elaborate park system is beloved but comes with a history of squabbles over who should manage it and who should pay for it. The state has for years sought to wean the Greenway off public funds, and Gov. Charlie Baker told the Herald after the report surfaced this week that he hopes it will stop using taxpayer money “in the not so distant future.”

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The Greenway hosts all kinds of art projects on the mile-and-a-half-long ribbon of landscaped grassy area that stretches from Chinatown to the North End.

Right now, the Greenway is host to a sculpture from Chinese artist Ai Weiwei called “Circle of Animals/Zodiac heads.” It features the heavy metal noggins of twelve creatures on poles.

When there are call-outs for art to be featured on the Greenway, competition is steep.

The Rose Fitzgerald Kennedy Greenway was born out of the Big Dig, as was the underground O’Neill Tunnel on which it sits. It replaced the much-despised Central Artery with public space filled with fountains, swings, trees, flower beds and seating areas. Dewey Square Park, the wide-open portion of it that sits across the street from South Station has been home to everything from Occupy Boston campers to Bernie Sanders rallies to the weekly Boston Calling beer-and-music block parties.