WASHINGTON (AP) — A bill to toughen federal safety regulation of oil and gas pipelines has passed the Senate after a Republican senator opposed to government regulation dropped his opposition to the measure.The bill was approved late Monday only a few hours after Sen. Rand Paul of Kentucky abruptly announced he was ending his opposition. He said in a statement that he was doing so because the bill's sponsors had agreed to incorporate an amendment regarding safety testing of older pipelines.Paul previously had told the bill's supporters his opposition was based on a philosophical objection to new regulation.The bill would increase penalties for safety violations, require the installation of automatic shut-off valves on new transmission lines and authorize more safety inspectors, among other provisions.