LONDON (AP) — An influential ratings agency downgraded BP yesterday because of worries about the continuing Gulf of Mexico spill, sending the oil company's shares to a new low.

Shares in BP fell below 350 pence for the first time since the oil rig disaster, dropping 2.5 percent to 346 pence ($5.12) by mid-afternoon on the London Stock Exchange.

Fitch Ratings downgraded BP's long-term issuer default rating and senior unsecured rating to BBB from AA.

"The scale of today's rating action has been partly driven by the increased risk that the balance between long-term and near-term cost payments may now be skewed much more heavily toward the near term than previously anticipated," Fitch said.

The ratings company said it was concerned by reports from US government scientists that the volume of the spill was significantly larger than previously indicated.