She speaks seven languages, has a PhD in particle physics, an apartment in Budapest plastered with her own pastel drawings, and a career that took her around Africa and Europe doing humanitarian work.

What Cristiana Barsony-Arcidiacono, 49, the Italian-Hungarian CEO and owner of Hungary-based BAC Consulting, says she hasn't done is make the exploding pagers that killed 12 people and wounded more than 2,000 in Lebanon this week.

After her company was revealed to have licensed the design for the pagers from their original Taiwanese manufacturer Gold Apollo, Barsony-Arcidiacono told NBC News that she didn't make them.

"I am just the intermediate. I think you got it wrong," she said.

Since then, she has not appeared in public. Neighbours say they haven't seen her. Barsony-Arcidiacono has not responded to calls and emails and there was no answer when reporters visited her private address in downtown Budapest. Her flat in a stately old Budapest building, where a door to a vestibule had been open earlier in the week, has been shuttered.

Hungarian intelligence services have conducted several interviews with Barsony-Arcidiacono, the Hungarian government said this weekend.

Taiwanese pager firm Gold Apollo said this week that the model of pagers used in detonations in Lebanon were made by BAC Consulting, adding it had only licensed out its brand to the company and was not involved in the production of the devices.

Hungarian intelligence agencies have been conducting their investigation and have interviewed Barsony-Arcidiacono several times, the Hungarian government's international press office said in a statement.

It quoted the Constitution Protection Office (AH), one of Hungary's intelligence agencies.

The AH reiterated an earlier statement from the government that said that the pager devices used in the mass detonations were never in Hungary.

Prime Minister Viktor Orban's government also said earlier that BAC Consulting was "a trading-intermediary company, which has no manufacturing or other site of operation in Hungary".

Discussions with acquaintances and former work colleagues paint a picture of a woman with an impressive intellect and a peripatetic career in a string of short-term jobs in which she never quite settled down.

An acquaintance of hers, who like others who knew her socially in Budapest asked not to be identified, called her "Good-willed, not a business type". The person said she appeared to be someone who is always enthusiastic to try something new and readily believed things.

Kilian Kleinschmidt, a veteran ex-UN humanitarian administrator who hired Barsony-Arcidiacono in 2019 to run a six-month Dutch-funded programme to train Libyans in Tunisia in subjects such as hydroponics, IT and business development, described hiring her as a big "mistake". After disagreements in how she managed staff, he said he let her go before her contract was over, which could not be independently verified.

At her Budapest home, a steel outer gate encloses a small vestibule where life drawings sketched in red and orange pastels can be seen taped up on the wall. An inner door leading into her apartment was ajar when reported first visited the building this week, and closed when the reporter returned the next day. No one answered the bell.

An office building where BAC Consulting KFT is said to be registered, in Budapest, Hungary. – Reuters

A woman living in the building for the past two years said Barsony-Arcidiacono was already a resident when she moved in, and described her as kind, not loud, but communicative.

She practised her drawing as part of a Budapest art club, though she hadn't attended for a couple of years, said the organiser of the group, who said she seemed like more of a businesswoman than an artist but was upbeat and outgoing.

A school mate of Barsony-Arcidiacono said she grew up in a family with a working father and housewife mother in Santa Venerina, near Catania in eastern Sicily, and attended high school nearby. He described her as a quite reserved youngster.

In the early 2000s she earned her PhD in physics at University College London, where her dissertation on positrons - a subatomic particle with the mass of an electron and a positive charge - remains available on the UCL website. But she appears to have left without pursuing a scientific career.

"As far as I know she has not done scientific work since then," Akos Torok, a retired physicist who was one of her professors at UCL and published papers with her at the time, said in an email.

A resume she used to get the job working for Kleinschmidt included references to other post-graduate degrees, in politics and development, from the London School of Economics and the School of Oriental and African Studies, which could not be independently verified.

She then went on to describe a string of jobs working on NGO projects in Europe, Africa and the Middle East.

In a separate CV on the BAC Consulting website, she described herself as a "Board Member at the Earth Child Institute", an educational and environmental charity in New York. The group's founder, Donna Goodman, said that Barsony-Arcidiacono had never held any role there.

"She was a friend of a friend of a board member, and contacted us about a job opening" in 2018, Goodman said. "But she was never invited to apply."

That CV also described her as a former "Project Manager" at the International Atomic Energy Agency in 2008-2009, who organised a nuclear research conference. The IAEA said its records indicated she had been an intern there for eight months.

On BAC Consulting's website, which was taken down by the end of this week, the company gave little idea of its actual business in Hungary. Its registered address is a serviced office in a Budapest suburb.

"I am a scientist using my very diverse background to work on interdisciplinary projects for strategic decision-making (water & climate policy, investments)," Barsony-Arcidiacono wrote on her CV.

"With excellent analytical, language, and interpersonal skills, I enjoy working and leading in a multicultural environment where diversity, integrity, and humour are valued."