DETROIT (AP) — Shares of General Motors Co. sank to a 10-month low Friday amid continuing fallout from a mishandled recall of 2.6 million small cars.

Standard & Poor’s raised doubts that GM’s credit rating would be restored to investment grade status this year after the automaker boosted its estimated for costs related to a series of recalls announced since February. And documents released by a House subcommittee raised further questions about GM’s handling of safety issues.