Package with what seemed to be an explosive was found in a mail box outside the billionaire financier’s house.

A package containing what appeared to be an explosive device has been found in a mailbox outside the New York residence of billionaire financier George Soros.

An employee at the home in Katonah, New York, opened the package, revealing what appeared to be an explosive device, police said on Monday.

Soros was not home at the time, the New York Times reported.

Soros, one of the world’s biggest donors to liberal groups and causes, has become a hated figure for right-wing campaigners in the United States and Eastern Europe, and the target of a hostile media campaign by the nationalist government in his native Hungary.

Authorities were contacted at around 3:45pm (07:45 GMT), the Town of Bedford Police Department said in a statement.

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Bomb squad technicians detonated the package in a nearby wooded area, police told the newspaper. The FBI was looking into the incident, police said.

A federal law enforcement official who spoke to The Associated Press news agency on condition of anonymity because he was not authorised to discuss the investigation said the device contained explosive powder.

Another federal official who also spoke on condition of anonymity said it resembled a pipe bomb and was in a package placed in a mailbox outside the gates of the compound.

A Soros employee opened it just inside the gates, nowhere near Soros’ quarters, the official said.

In a statement on Facebook, Soros’ Open Society Foundations (OSF) said the philanthropist deplored violence and urged “politicians across the political spectrum to tone down their rhetoric”.

The organisation blamed the US’ toxic political environment for the incident.

“The hateful rhetoric that dominates politics in the U.S. and in so many countries around the world breeds extremism and violence,” said OSF. “In this climate of fear, falsehoods and rising authoritarianism, just voicing your views can draw death threats.”

A Hungarian government spokesman said: “The matter falls under the jurisdiction of US authorities. After all, the incident occurred there.” He declined to comment further.