Updates share price in seventh paragraph and adds BP response on Hayward in 10th. For more on the Gulf of Mexico spill, see {SPILL .}

July 26 (Bloomberg) -- BP Plc returned to work on permanently plugging the source of the largest oil spill in U.S. history after a storm threat eliminated an opportunity to seal the Gulf of Mexico gusher more securely by the end of July.

The so-called static kill will pump mud from the top of the Macondo well next week, National Incident Commander Thad Allen said yesterday. That will be followed by mud and cement injections from the bottom using a relief well.