Narrative:

Was on first break. Asked to return to cockpit prior to its completion. Flight manual procedures for smoke/fumesecond officerdor was in progress. Source of fumes could not be determined. Declared emergency and requested clearance to ZZZZ. All checklists were completed. Descent was normal. Accomplished overweight landing at ZZZZ.

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Original NASA ASRS Text

Title: A B767-300 FLT CREW ON AN INTERNATIONAL FLT EXPERIENCED FUMES IN THE COCKPIT. THEY DECLARED AN EMER AND DIVERTED TO THE NEAREST SUITABLE ARPT.

Narrative: WAS ON FIRST BREAK. ASKED TO RETURN TO COCKPIT PRIOR TO ITS COMPLETION. FLT MANUAL PROCS FOR SMOKE/FUMES/ODOR WAS IN PROGRESS. SOURCE OF FUMES COULD NOT BE DETERMINED. DECLARED EMER AND REQUESTED CLRNC TO ZZZZ. ALL CHKLISTS WERE COMPLETED. DSCNT WAS NORMAL. ACCOMPLISHED OVERWEIGHT LNDG AT ZZZZ.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.