A carriage horse that collapsed and died while carrying two tourists in New York's Central Park last week had eaten a toxic piece of shrubbery, according to a necropsy released by the transport workers' union.

The animal had ingested a foliage from a Japanese Yew, the report by Cornell University College of Veterinary Medicine, which was circulated by the TWU Local 100, said. 

The incident has reignited a long-running dispute over whether the horses, which have been a favorite of many visitors since Central Park opened in 1858, should be banned. 

The horse, named Deniz, was under the care of carriage driver Nurettin Kirbiyik on the East Drive of the park on Tuesday 9 June when the animal collapsed and died.

The necropsy report revealed 'abundant plant needles' in the horse’s stomach, mouth and digestive tract. Kirbiyik saw 'no signs' that the horse had been unwell before it collapsed, according to the report put out by TWU Local 100. 'I feel like I lost someone in the family,' he said.

Animal rights groups have long campaigned for traditional horse and carriages to be banned from operating in Central Park over concerns for their welfare. 

NYC mayor Ed Koch was the first to implement limited protections for the horses back in the 1980s. Bill De Blasio ran on removing them from the park entirely in 2013, but failed to implement a ban after taking office.

TWU Local 100 officials on Tuesday blamed the Central Park Conservancy for planting the shrubs, noting that Japanese Yew, which is widely present is extremely toxic to both horses and humans. The plant can cause cardiac arrest and death. 

The union also demanded an apology from New Yorkers for Clean, Livable, and Safe Streets (NYCLASS), the main group that has long protested the carriage horse industry, as well as local lawmakers.

TWU Local 100 shop steward Christina Hansen said the carriage horse drivers cannot always control what their animals eat while they walk around the Central Park loop.

'We are supervising them, but a toddler just as easily could have ingested some of this plant,' she said, according to a report by Gothamist. 'The fact that it was anywhere within reach of a horse that was on the carriage drive, which was designed for horses to be on, is outrageous.'

In a statement Central Park Conservancy's Kate Blumm said Japanese Yew is commonly planted across the US and that it is the responsibility of horse carriage operators to stop their animals from grazing on park plants.

'This tragedy underscores something larger: It’s time for New York City to join other major cities around the world and ban horse carriages from our city,' Blumm added.

The pushback by Local 100, an influential union that also represents a majority of New York City’s transit workers, comes as some lawmakers are pushing to pass a bill to abolish the carriage horse industry.

'TWU’s own statement demonstrates a complete failure to properly supervise and protect a horse in their care,' said Edita Birnkrant, executive director of NYCLASS, per the outlet.

Mayor Zohran Mamdani has said he thinks that carriage horses should be banned from the park, but has also said he wants to work with the drivers union to protect their jobs and find a solution that appeases both sides.

Daily Mail reached out to TWU Local 100, Central Park Conservancy, NYCLASS, and Mayor Mamdani's office for comment.