Soros, one of the world’s biggest donors to liberal groups and causes, has become a hate 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.

An employee at the home in Katonah, New York, opened the package, revealing what appeared to be an explosive device. Soros was not home at the time, the New York Times reported.

Authorities were contacted at around 3.45pm, the Town of Bedford Police Department said in a statement.

Bomb squad technicians detonated the package in a nearby wooded area, police told the newspaper.

The Federal Bureau of Investigation was looking into the incident, police said.

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.