A French police source told Reuters that up to 26 million euros ($32 million) could have been taken.
The 22-year-old daughter was released after the heist on Thursday night, Vaud police said.
The three men responsible for the robbery escaped in a dark-coloured luxury sport-utility vehicle from a parking lot at Chavornay, located north of Lausanne, where the van had been forced to park before being emptied, they added.
"The thieves fled to an unknown destination. The daughter of one of the security guards was held hostage in France but then released. No one was injured," Vaud police said in a statement that gave no estimate of the amount stolen.
Jean-Christophe Sauterel, chief cantonal police spokesman, said two security guards had been in the van, which was found abandoned in a parking lot.
The suspects, who were armed, wore hoods and gloves and spoke French with an accent from southern France or possibly North Africa, he said.
"Regarding the motives, or the details on how the events exactly unfold, I can't give any other information for the moment," he told Reuters.
A French police source, confirming a report on French radio Europe 1, told Reuters in Lyon, France, that the armoured van was believed to be carrying 15 to 30 million Swiss francs (13-26 million euros) in cash.
Europe 1 reported the woman had been held hostage by men pretending to be plumbers at her home in Lyon.
Twelve Swiss police patrol cars and investigators were deployed in the operation and a criminal case has been opened, the Vaud police statement said, appealing for witnesses.
($1 = 0.8177 euros)
(additional reporting Catherine Lagrange in Lyon, France; writing by Stephanie Nebehay,; editing by Mark Potter)
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