US police arrested a Yale University laboratory technician accused of strangling a promising young scientist and hiding her body in a wall.

Raymond Clark (24) was arrested at a Connecticut motel, then arraigned in New Haven, where the Ivy League university is located, with bail set at $3-million.

The alleged killer, whose forearms are ringed with tattoos and who appeared in a polo shirt and pair of khaki trousers, said nothing before being led away again into detention.

Clark was declared a "person of interest" in the shocking case soon after Annie Le's body was discovered Sunday, stuffed into a wall cavity in the high security lab where he was a technician and Le worked as a graduate student.

Le, also 24, had been due to marry that day. She'd been missing since 8 September, but it took police five days to discover her corpse in the lab complex.

Police briefly detained Clark late on Tuesday and took a DNA sample to compare to physical evidence at the murder scene. Police would not confirm that the DNA samples matched.

On Wednesday, the Connecticut state coroner said that the cause of death was "traumatic asphyxiation due to neck compression".

The case horrified the prestigious university, alma mater of former president Bill Clinton, and a string of other politicians, business leaders and Hollywood stars.

Yale president Richard Levin said Clark had been at the lab since December 2004 and that "nothing in the history of his employment here gave any indication that his involvement in such a crime might be possible".

Urging calm, Levin said "we must not let this incident shatter our trust in one another".

"What happened here could have happened anywhere. It says more about the dark side of the human soul than it does about anything else," he added.

Possible motives behind the murder

New Haven Police Chief James Lewis told journalists that the murder highlighted the issue of workplace violence, something he called "a growing concern around the country".

"We have to really educate ourselves about who we work with and how we deal with each other," he said.

One newspaper reported that Clark had been upset by Le's handling of mice in the laboratory, where experiments on animals are performed. Other reports suggested that Clark may have been attracted to the petite Vietnamese-American student.

But Jeffrey Ian Ross, a criminologist at the University of Baltimore, said Clark made a puzzling suspect, given his clean record.

"Twenty-four years old is pretty old to be showing anger," Ross said.

Most such killings, he added, are over "love, money or some sort of disrespect".

It's also possible that the "perpetrator may not have gone into the interaction with the intent of killing the person, but in the heat of the moment things go from bad to worse, a struggle ensues and the person is killed," Ross said.

Police were initially mystified by Le's vanishing inside the strictly controlled laboratory.

All exits are covered by video cameras and it was clear that Le had entered the building, then never left.

Police examined hundreds of hours of security camera footage and questioned every person who was present in the building. Some 150 pieces of evidence were collected at the crime scene.

But repeated searches failed to discover the body until a dog trained in sniffing for cadavers found her remains stuffed in a wall cavity of the type used for electric cabling.

AFP

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