HOUSTON, July 23 (Reuters) - Chevron ( CVX ) on Tuesday

said recent testing indicates that zinc levels in flagship U.S.

offshore crude Mars' production stream were now within expected

levels.

The start-up of an offshore well caused zinc contamination in

Mars crude, Chevron ( CVX ) had said earlier this month, leading to

tightening crude oil supply in the key Gulf Coast refining hub

and the government releasing barrels from its emergency

stockpile.