The tooth of assassinated Congolese national hero Patrice Lumumba, pilfered by a Belgian police officer and ceremonially returned to the country in 2022, was potentially stolen on Monday.

A break-in at former Prime Minister Lumumba’s mausoleum in the Congolese capital left the glass doors smashed and broke the coffin containing the only lasting remains of the independence leader, according to Congolese news agency ACP.

The Congolese Ministry of Culture on Tuesday called the vandalism an “unacceptable act” and vowed to take “firm measures” to punish those responsible.

“All necessary measures are in place to restore the mausoleum as soon as possible,” the ministry added.

Culture Minister Yolande Elebe could not confirm to AFP whether the tooth had been stolen. “We have to wait for the police investigation to find out more,” she said.

Lumumba, the first democratically elected leader of Congo and an icon of the nation’s independence, was assassinated in 1961 and his body dissolved in acid by separatists and Belgian police officers.

His only remains, a single gold-crowned tooth, was kept in Belgium thereafter until it was handed over to Lumumba’s descendants in 2022 by Belgian Prime Minister Alexander De Croo in an effort to smooth relations with the Democratic Republic of Congo, a former Belgian colony.

“In the presence of [Lumumba’s] family, I would like to apologize on behalf of the Belgian government,” De Croo said then, adding that Belgian ministers in the early 1960s bear “moral responsibility” for Lumumba’s torture and murder.

The tooth was taken on a tour around Congo before it was interred at a mausoleum in the capital, Kinshasa.

Congo was a Belgian colony for more than half a century, from 1902 until its independence in 1960. Prior to that, King Leopold II of Belgium brutally occupied the country, carrying out a forced labor regime and killing up to 10 million people.

Numerous former colonies in Africa and elsewhere have demanded reparations and the return of stolen artifacts from their former occupiers in recent years, from Namibia to India.