The move late came less than a week after the French branch of Switzerland's largest bank was also placed under investigation — the closest equivalent in France to being charged.
The alleged offences date back to the 2000s.
Investigators suspect UBS allowed its Swiss staff to illegally approach French clients, and to have set up a shadow accounting system to hide movements of capital between France and Switzerland.
"The tribunal's decision widens the probe," UBS said in a statement in French.
"UBS will continue to cooperate with the French authorities," the bank said, adding that it would not allow "any move aimed at helping clients to avoid their fiscal duties."
A former head of UBS France, Patrick de Fayet, a former head of the bank's office in the northern French city of Lille and a UBS executive in the eastern city of Strasbourg are already under investigation.
The French probe was launched after allegations from a former UBS employee turned whistleblower.
An anonymous note seen by AFP that was sent to the ACP, the Bank of France's regulatory arm, alerted the body to the parallel accounts that ran between 2002 and 2007. These listed accounts were opened in Switzerland by businesses but not declared in France.
The investigating magistrates handling the UBS affair have sent a list containing 353 names of people suspected of having held a Swiss account and have requested details from the Swiss authorities.