UPDATE 3-Luxembourg launches probe into Espirito Santo holding companies
* Finance minister says no threat to financial stability
* Portugal Telecom shares fall sharply, Oi also hit
* Banco Espirito Santo falls 11 pct, ESFG 18.5 pct (Adds finance minister comment)
By Robert-Jan Bartunek and Andrei Khalip
BRUSSELS/LISBON, June 27 (Reuters) - Luxembourg's justice authorities have begun an investigation into three holding companies of Portugal's Espirito Santo banking family, the biggest shareholder in Portugal's largest listed bank which bears their name.
A spokesman for the Luxembourg authorities said the investigation was launched on May 22 over alleged breaches of company law by the three Luxembourg-registered firms. He declined to give any further details about the investigation.
"The judge is investigating this now and during this time no further statements can be made," the judicial spokesman said.
Shares of Banco Espirito Santo (BES) and ESFG - the only listed holding company of the three - as well as Portugal Telecom, which acknowledged it had bought debt from another family holding company, fell on Friday.
Meanwhile, Finance Minister Maria Luis Albuquerque said the bank was well-capitalised and the government saw no threat to financial stability and public accounts. Continuación...