Australian university professor Lily Pereg and her sister have been found dead after disappearing more than two weeks ago in Argentina.

Key points: Dr Pereg was highly experienced in the field of plant and soil microbiology

Dr Pereg was highly experienced in the field of plant and soil microbiology The family has expressed their "shock" over the "huge tragedy"

The family has expressed their "shock" over the "huge tragedy" Tributes to Dr Pereg have described her kindness and friendship

Dr Pereg, 54, a microbial ecologist at the University of New England, and her sister, Israeli citizen Pyrhia Sarusi, 63, were last heard from on January 11 after travelling to the country to visit Ms Sarusi's son.

Their bodies were found on a lot beside the home of Ms Sarusi's son Gilad Pereg, near the city of Mendoza, on Saturday (local time).

Prosecutor Claudia Rios confirmed that Mr Pereg had been arrested on homicide charges, adding that an autopsy would determine the cause of death.

A GoFundMe page that had been established to raise money to search for the women carried a message from the family expressing their "shock" over their alleged murder.

"The family are … humbled by the outpouring of support and love, worldwide," it said.

"Your love carried us and will help us recover from a huge tragedy. There will never be an explanation."

Dr Pereg had 25 years of research experience in plant and soil microbiology and had supervised dozens of PhD, Master and honours students in microbiology, according to the University of New England's website.

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She obtained a PhD from the University of Sydney in 1998 and worked at the University of Cologne, in Germany, before joining UNE in 2001.

She chaired the soil, microbiology and biodiversity subdivision of the European Geosciences Union.

Tributes have begun pouring in for Dr Pereg on a Facebook page that had initially been set up to aid in the search.

One woman wrote that she was "devastated" by the death of her friend and colleague.

"She had been a wonderful presence and highly regarded in her field of research," the post said.

"For me and many others, a beautiful friend."

Argentine authorities said the cause of death was still being determined. ( Facebook )

Others wrote of her kindness, with one man posting "the world is a lesser place without people like her".

One woman, who had posted several photos with Dr Pereg "spending 16 years together in one of the most beautiful friendship", said she had been "still hoping for their return".

"I am devastated like all of their family and friends. Nothing will bring them back now," she wrote.

The family's message thanked police in Argentina, Australia and Israel as well as consular officials for providing support and sharing information with the family.

"We will bring the sisters home for the last time, and will let you know when and where," it said.

At the time of writing, the fundraising campaign had raised more than $7,500. Unused funds would be donated to charity, the message said.

Emeritus Professor in Agricultural Chemistry and Environmental Chemistry, Ivan Kennedy from the University of Sydney, said he mentored Dr Pereg when she attended the university in the 1990s.

"She has always shown this wonderful promise so this just elevates this tragedy of her life ending so unexpectedly," he said.

Tatum Scharkie, a third-year microbiology student from the NSW Central Coast, said she was deeply saddened by the news.

"It is absolutely horrific, when I first found out it was a like a hole in my stomach and my heart. It was horrible she had gone missing — you do not want to think the worst, but that is at the back of your mind," she said.

ABC/wires