TREASURIES-Bond losses grow after Philly Fed data

(Updates with reaction to Philly Fed data)

NEW YORK, June 18 (Reuters) - U.S. Treasury debt prices added to their earlier fall on Thursday after an index of business conditions in U.S. Mid-Atlantic states turned much less negative, suggesting stabilization in the factory sector.

The Philadelphia Federal Reserve's business activity index came in at minus 2.2, its least negative reading since September 2008. This compares with minus 22.6 in May and analysts' median forecast of minus 17.0.

A negative reading signals business contraction in the Mid-Atlantic region.

The price of benchmark 10-year notes US10YT=RR was down 19/32, versus a 9/32 fall prior to the Philadelphia Fed report.

Their yield, which moves inversely to price, was 3.77 percent, up from 3.73 percent shortly before the data. It ended at 3.70 percent on Wednesday. (Reporting by Richard Leong; Editing by James Dalgleish)