Shares of BP fell Monday after it said the tab for the Gulf of Mexico oil spill is nearing $4 billion while it monitors seepage near the ruptured well.
BP PLC's shares lost $1.47, or 4 percent, to close at $35.63.
Investors remain worried about the mounting costs and whether the latest fix will hold until a relief well is in place, Argus Research analyst Phil Weiss said.
"If the well integrity is compromised, it makes the process more complicated," he said.
The cost of dealing with the oil spill — almost $4 billion — equals about two-thirds of BP's profit in the first three months of the year.
BP put a cap on the well Thursday, shutting off oil that had been gushing from it since the Deepwater Horizon rig exploded April 20 and then sank. Seepage detected from the sea floor near the well prompted new concern about whether the fix would hold.
The government is allowing BP to continue monitoring the site for new leaks, at least for now.
Key questions remain about BP's liability, Credit Suisse analyst Kim Fustier said.
In a research note to clients on Monday, Fustier said yet to be determined is the total cost for liability and compensatory claims and how the liability costs will be distributed between BP and its partners.
If negligence is proven, another issue could be punitive damages, the analyst said.
Shares of Transocean, owner of the doomed rig, lost $4.02, or 7.7 percent, to close at $48.06. Shares of Anadarko Petroleum, which has a 25 percent stake in the well, dropped $1.94, or 4.1 percent, to close at $45.52. Halliburton, which reported better-than-expected earnings on Monday, rose $1.66, or 6 percent, to close at $29.17. Cameron International gained $1.64, or 4.7 percent, to close at $36.39.
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