MOSCOW, May 29 (Reuters) - An incident at the Tengiz field, Kazakhstan's largest and operated by Chevron, caused a sharp drop in production on May 26, two industry sources told Reuters on Friday.

The two sources added that daily production at the Tengiz field, which had just recovered from a previous incident, fell to between 5,000 and 10,000 tons on Tuesday, compared to the usual level of 125,000 tons or 995,000 barrels.

The two sources spoke on condition of anonymity due to the sensitivity of the matter and without providing any details about the incident or its causes, but they expected oil production to gradually resume within about a week.

A third source said that production at the field had returned to about 82,000 tons on May 27.

Chevron said in a statement today that part of the Tengiz oil field experienced a "minor operational disruption" on May 28 and production levels are being restored.

Production at the Tengiz field, located near the Caspian Sea in far western Kazakhstan, was not fully resumed until April, after being halted in January due to a power distribution problem.