Shares in BP PLC are plunging in London after the oil company's failed attempt to block the oil leak in the Gulf of Mexico.

Shares fell 13 percent Tuesday to 429.2 pence ($6.20) on the London Stock Exchange. It is the first day of trading there since the failed attempt over the weekend.

BP also said that costs for the spill have reached $990 million.

The company is now attempting to use remote-controlled submarines to cut pipes before placing a containment cap over the leak. The spill, which has dumped between 18 and 40 million gallons into the Gulf, is the biggest in U.S. history