RPT-UPDATE 3-EU opens probe into Thomson Reuters coding tool

* EU says probe doesn't imply proof of antitrust violation

* EU says probe launched on its own initiative

* Thomson Reuters says cooperating with EC

* EU says competitors do not have similar restriction

* Shares close down less than 1 pct (Adds analyst's note, background on S&P, CUSIP, changes dateline, previous BRUSSELS)

By Foo Yun Chee and Robert MacMillan

BRUSSELS/NEW YORK, Nov 10 (Reuters) - EU antitrust regulators launched an investigation on Tuesday into how Thomson Reuters (TRI.TO)(TRI.N) codes its financial market data feeds, saying it might discourage customers from moving to rival firms.

The European Commission, which polices competition in the 27-country European Union, said it had launched the investigation on its own initiative and it did not imply that it had proof that Thomson Reuters had broken the law.

The Commission said it would examine whether Thomson Reuters could prevent clients from mapping Reuters Instrument Codes (RICs) to identification codes of other datafeed suppliers.