It's harder to find the news articles discussing the early efforts to close the valves because it's not exactly news anymore, but here's what wikipedia says.
"The rig's blowout preventer, a fail-safe device fitted at source of the well, did not automatically cut off the oil flow as intended when the explosion occurred. BP attempted to use remotely operated underwater vehicles to close the blowout preventer valves on the well head 5,000 feet (1,500 m) below sea level, a valve-closing procedure taking 24–36 hours. BP engineers predicted it would take six attempts to close the valves. As of May 2, 2010, they had sent six remotely operated underwater vehicles to close the blowout preventer valves, but all attempts were ultimately unsuccessful."
