Reports said Austrian authorities would order an autopsy. "Everything points towards a suicide, and there are no signs of any third party being involved," a police spokesman, Alexander Haslinger, told the French news agency AFP. Authorities in Vienna have privately indicated to other governments that while suicide is the principal cause of death under investigation, they haven't ruled out the possibility that it could have been an accident or even murder, according to an official source in Washington. Official reports and a former U.N. official indicate that Hampton fell 12 stories down an internal emergency stairwell—from the 17th to the fifth floor—in the high-rise Vienna building.

Some news reports said that Hampton had been involved in the current round of negotiations between Iran, the U.S., and several other Western countries regarding Tehran's controversial nuclear program. However, his participation in the Iran talks could not be immediately confirmed, and a former U.N. official who worked at the Vienna complex said that officials who worked for the CTBTO were normally not supposed to have any involvement with the work of the IAEA, which is based in the same complex and is at the center of diplomatic discussions between the West and Iran.

CTBTO literature says that Hampton, who was to turn 48 on Wednesday, had worked for CTBTO for more than 10 years and had previously worked in Britain on "test-ban monitoring issues." Hampton was one of four coauthors of a  paper published by CTBTO last month regarding seismic readings taken during the course of a North Korean nuclear test last May. There is some apparent historical resonance between this case and the death of Dr. David Kelly, a British government scientist who killed himself in July 2003 after he fell under suspicion for potentially leaking information that raised questions about the intelligence used by the British government to justify its support for the invasion of Iraq. Kelly's death ultimately was the focus of a full-scale investigation by a senior British judge, which found that the BBC misreported allegations that Tony Blair's government had "sexed up" an anti-Saddam Hussein dossier, but also revealed evidence of political pressure on British intelligence officials to come up with alarming information about Saddam's alleged weapons of mass destruction program.