Big French companies have been gorging on cheap debt in recent years with bank loans up 5.4 percent in September, twice as much as the euro zone average, according to the Bank of France.
"For now we don't see financial bubbles at the euro zone level, (but) there are worrying small signs, in France for example," Coeure, who is a member of the ECB's Executive Council, said in an interview with franceinfo television.
"Corporate debt is rising very fast, which is something we are watching. But there is nothing today that justifies that the ECB withdraw its support for growth," he added, speaking in Lyon ahead of an economics conference.
Last month, the ECB said it would reduce its bond purchases from January as the euro zone economy was recovering, although it still needed support.
The Bank of France is also taking a close look at corporate credit growth in France and has said it could take measures to rein it in if deemed necessary.
(Reporting by Leigh Thomas; Editing by Sudip Kar-Gupta)