Over 100 Peace Corps volunteers have been pulled out of Kazakhstan, the BBC reported.
The decision was announced just over a week ago and the last of the program's 117 serving volunteers sent back to the US this weekend.
Kazakh authorities said their services were no longer needed, but other reports indicated that volunteers had been told to leave for their own safety, the BBC said.
Kazakhstan's Ministry of Education and Science said the suspension of the Peace Corps program was a "logical step" given the country's "great progress in the political and socio-economic development," EurasiaNet reported.
Meanwhile the Peace Corps cited "a number of operational considerations" for its decision to end its 18-year program, but gave no further details.
More from GlobalPost: Peace Corps volunteers speak out against rape, sexual assault
Deputy Communications Director Kristina Edmunson told the Wall Street Journal that the decision followed "several incidents in Kazakhstan in recent months involving individual volunteers."
Volunteers themselves suggested that an increase in sexual assaults could be the reason for their abrupt departure.
On her blog, former volunteer Rebecca Gong wrote:
"There have been 5 sexual assaults or rapes this year within Peace Corps Kazakhstan, which indeed ranks it first worldwide among PC countries for such incidents. [...] if you were a girl who signed up for PC KZ last year, you had a roughly 8.3% chance of being raped."
Others speculated that the Kazakh government was hostile to the presence of US volunteers.
"It seems to be a combination of security concerns and growing government resistance," wrote volunteer Michael Hotard on his blog, claiming that volunteers were regularly subjected to phone-tapping, accusations of espionage and investigation by the state police.
A leaked diplomatic cable referred to a 2008 incident in which a Peace Corps volunteer was arrested in northern Kazakhstan in possession of explosives as a "Soviet-style set-up," aimed at "discrediting the Peace Corps and damaging bilateral relations," said EurasiaNet.
In May 2011, the Peace Corps admitted it had not been "sufficiently responsive" to attacks on its volunteers following several reports of rape and one murder, the BBC reported. On November 21, President Barack Obama signed a law requiring the Peace Corps to better protect whistleblowers and offer mroe help to victims of sexual assault, ABC News said.