BANGKOK — A historic monument that commemorated government victory over a pro-monarchy rebellion eight decades ago was removed Thursday night without notice or explanation.

Activists and historians fear that the Constitution Defense Monument, which stood at the Laksi Intersection in northern Bangkok, could be destroyed after security forces were seen taking it away in the early hours. Officials declined to comment on its fate.

“We don’t know where it is now. There’s a risk that the monument will be gone for good,” said Chatri Prakitnonthakarn, a conservationist who teaches history of Thai architecture at Silpakorn University.

Read: Could Democracy Monument Be Razed? It’s Been Tried Before.

It’s the second time in two years a physical reminder of democracy in Thailand has been removed in secret and without explanation. In April 2017, a plaque commemorating the 1932 revolution that ended absolute monarchy disappeared from the Royal Plaza and was replaced with one extolling the monarchy.

Chatri said he fears that the same fate is befalling the monument as the plaque.

Speaking by phone Friday just hours after the monument was removed, he said he thought there would be no further relocation of the monument after it was already relocated in 2016 to make way for construction of a new skytrain line.

“This was done in haste. Everyone thought the location it was moved [until today] was its new permanent location,” he said.

The memorial was built in 1936 to protect the newly established constitutional democracy from a failed royalist revolt led by Prince Boworadet in 1933. The rebels sought to restore absolute monarchy, which had come to an end a year earlier.

Bang Khen district chief Somboon Homnan maintained he didn’t know anything about the removal. He said the monument was located in an area governed by the state railway, which is building an elevated railway nearby.

“I just heard about this for the first time from you,” Somboon said to a reporter.

MRT deputy governor Surachet Laophulsuk, who oversees the railway construction project, declined to comment. Junta spokesman Col. Winthai Suvari could not be reached as of publication time.

One witness to the monument’s removal was pro-democracy activist Karn Pongpraphapan, who went to the site Thursday night after hearing about the sudden operation.

Karn said police confiscated his phone at about 3am Friday just as he was trying to begin a live video stream via Facebook Live.

In an interview, Karn said one of the soldiers at the scene refused to tell him why the monument was being removed.

“He only said one word: ‘secret,’” said Karn.

In November 2014, months after the May 2014 coup, another monument commemorating Thailand’s first constitution in Buriram province was also torn down. Local officials said the memorial blocked traffic.

Additional reporting Teeranai Charuvastra

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