UPDATE 1-Colonial Pipeline reports Tennessee gasoline spill

(Adds recent status)

NEW YORK, Oct 5 (Reuters) - Colonial Pipeline, the nation's largest oil product pipeline, said on Thursday one of its stublines carrying gasoline from Atlanta to Nashville may have had a release of about 500 gallons, necessitating the shutdown of Line 19.

In a note sent to shippers late Thursday, Colonial said repairs on Line 19 were under way and the initial estimated restart time has been delayed as external damage to the pipe was discovered.

The line was shut on Wednesday after an odor of gasoline was reported near its Moccasin Bend Delivery unit in the Chattanooga, Tennessee, area.

Line 20, a distillate line running parallel to Line 19, was also shut as a precaution.

"Additional excavation of Line 20 will also be required prior to its restart to ensure its integrity," the pipeline operator said.

(Reporting By Janet McGurty in New York and Soma Das in Bangalore; Editing by Prateek Chatterjee)

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