From Hugh Schofield in Paris

HE was a successful engineer for an American car equipment company who liked to host barbecues and dabbled in amateur dramatics. She was a housewife who looked after their two children, practised yoga and helped out in the kindergarten of the lyce. Both were pillars of the French expatriate community in Seoul.

But now Jean-Louis and Veronique Courjault are on the run from the South Korean police. From their home in Tours, central France, they have made clear they will resist attempts at extradition. Their lawyer protests their innocence - indeed their bafflement at all that has happened. And yet the questions persist: whose are the two dead babies found in the freezer of their suburban Seoul home? How did they die? And when?

The macabre mystery began on July 23 when 40-year-old Jean-Louis Courjault interrupted his family holiday in France to return to Seoul "for urgent professional reasons".

Unused to shopping for himself, he bought some mackerel which he intended to freeze. Opening the freezer, he made the horrific discovery: two babies, weighing just over seven and eight pounds, wrapped in towels and then placed in plastic bags on two separate drawers.

According to later police reports, the packages bore traces of meconium - the greenish faecal matter which forms a baby's first bowel movement - and small parts of umbilical cord were also found. In other words the babies were newborn when they died, though whether they were twins remains unclear.

Courjault went immediately to the police, disclaiming all knowledge. He gave a specimen of saliva for genetic testing, and was then allowed to return to France.

Three weeks later the affair exploded in Korea, when - according to the authorities - DNA analysis revealed that Jean-Louis was indeed the father of the babies. Strands of hair taken from the couple's bathroom were then tested, and revealed that Veronique, 39, was also the mother - a conclusion that was apparently confirmed after doctors compared tissue samples taken in a local hospital when Veronique underwent a hysterectomy in December 2003.

"The chances of the woman not being the mother of these babies are absolutely nil," a police officer in Seoul told journalists.

The Korean police are operating on the hypothesis that - with or without the knowledge of her husband - Veronique disposed of the babies sometime before her hysterectomy, which they believe may have been occasioned by a problem pregnancy. They have asked the French authorities to be allowed to interview Veronique as a suspect, but so far the case is blocked because the necessary papers have yet to be translated.

French state prosecutor Sylvie Pantz said it was impossible to open an enquiry in France, "because for now we have absolutely no proof that the babies ever drew a breath. How do we know they were killed? And if they were killed, then how? Strangled, suffocated? The South Koreans can say they've got the DNA of the Courjaults, or of Jean-Marie Le Pen, or of the Pope - but until we have documents, we can do nothing."

And in the meantime, the couple deny categorically that they are the parents of the frozen babies. In a press conference, Jean-Louis said he "could not understand the results of the DNA tests. We are completely overcome by what has happened. It is a nightmare. My wife never gave birth to these two children."

Neighbours of the Courjaults in the leafy Sorae village neighbourhood of the Korean capital described them as a model couple, who from their arrival in 2002 took an active part among the growing French community. Jean-Louis recently played the role of a police inspector in a French murder mystery play put on by a local group, and Veronique was taken on as a childminder a year ago. Nobody can remember seeing her pregnant.

"After the rehearsals we would often go back to eat at their house, and it was totally informal. We were in and out of their cupboards - and their freezer," said Patricia Crozel, who refuses to believe the accusations against the couple.

"You can show me all the DNA tests you like. I have been with them often enough to know they are incapable of a horror like this,"she said.

According to Jean-Louis, "there are also sorts of other possible explanations for what has happened".

His lawyer has raised the idea that it could be part of a destabilisation plot linked to Jean-Louis's work as an engineer. Korean investigators are less than convinced.