The disappearance of a British-Cypriot woman who was last seen Monday going for a run on a Greek island has prompted a massive search, police said.

Natalie Christopher, 34, an astrophysicist who lives in Cyprus, was first reported missing by her 38-year-old partner, with whom she had been vacationing on the Greek island of Ikaria, The Telegraph reported.

She left him a note saying she was going for a run, but failed to return, he said. The couple were planning to return home to Cyprus that evening.

Police, firefighters, Coast Guard officers, volunteers and a helicopter crew were participating in the search for Christopher. Police said they were keeping all lines of inquiry open.

“We are investigating every possibility, every scenario,” police spokesman Theodoros Chronopoulos told The Guardian. “At this stage, we’re not ruling out anything.”

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Christopher's Facebook account indicates she is active in hiking, running, and mountain racing. An Oxford graduate, she is a researcher at the European University Cyprus.

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Christopher’s case comes on the heels the death of American scientist Suzanne Eaton, whose body was found in an abandoned World War II bunker on the Greek island of Crete last month.

Eaton, a 59-year-old molecular biologist at the Max Planck Institute in Dresden, Germany, had been on the island for a conference and disappeared while out for a run.

A 27-year-old local man has been charged with rape and murder in Eaton's death.

Fox News’ Travis Fedschun and The Associated Press contributed to this report.