PHNOM PENH (Reuters): The United States embassy in Cambodia has fired 32 people caught allegedly sharing pornographic material in a non-official chat group, several sources familiar with the matter said on Friday.

Four sources told Reuters that pornographic videos and photographs, including some featuring people under the age of 18, were shared in a Facebook Messenger chat group.

Some of the images were seen by the wife of an embassy worker who reported the incident to an official at the embassy. The matter was then forwarded to the Federal Bureau of Investigation (FBI), the sources said.

"They had their identification cards taken and some of their phones checked," a former US embassy staff member told Reuters on condition of anonymity.

He said the 32 embassy workers included Cambodians and Cambodian-Americans. Many were guards and some were clerical staff. There were no diplomats among them, they said.

Two of the sources, both of whom work at the embassy, confirmed the dismissals.

The dismissals come at a time of tension between Cambodia and the United States over US criticism of a crackdown on dissent by long-serving Prime Minister Hun Sen, and his anger over what he says have been US efforts to undermine his rule.

The United States has denied interfering in Cambodian politics. The Cambodian government has not commented on the dismissals.

Cambodia, still emerging from decades of conflict and poverty, has been notorious for child prostitution, and several foreigners have been convicted and jailed for child abuse in recent years.

Child rape continued to be a serious problem in Cambodia, the US State Department said in a 2016 report.

An embassy spokesman said he could not comment and referred queries to the State Department. The State Department declined to comment when contacted by Reuters.

"These records are confidential," a State Department official told Reuters on Friday.

"I am not sure that's really something we would have comment on," he said.

Reuters could not contact any of the workers who had been fired. The FBI could not be reached for comment and Cambodian police spokesman Kirth Chantharith also could not be reached for comment.

It was not immediately possible to get a figure for the number of people employed at the embassy, which is housed in a purpose-built, city-centre compound.