Five Star Quality Care Inc., an operator of nursing homes and assisted-living facilities, said Wednesday that it started an offering of 10 million shares and will use proceeds to repay a bridge loan and fund acquisitions.

The Newton, Mass., company said underwriters will have an option to buy an additional 1.5 million shares to cover any excess demand. Joint book-running managers for the offering are Jefferies & Co. Inc., Citi and UBS Investment Bank.

Shares of Five Star Quality Care fell 39 cents, or more than 5 percent, to $6.81 in after-hours trading.