It happened Wednesday afternoon at a manhole on Park Avenue between East 69th and 70th streets.
Asbestos was detected in debris that spewed from the leak, initially prompting city officials to ask residents to close their windows.
Tests on debris showed the presence of asbestos, but Con Edison said complete air sampling results were negative.
Ten nearby customers were without heat or hot water for part of the day Thursday.
Con Ed will continue with repairs as normal on the steam pipe.
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