HARRISBURG — Pennsylvania U.S. Sen. Bob Casey is back from a weeklong trip to Pakistan and Afghanistan to look into efforts to stop the roadside bombs that are killing and maiming American troops.

Casey said Wednesday that he expects to see casualties from the bombs decrease over time because of American advances in technology to detect them and to investigate their origin.

He met with Pakistan’s prime minister to urge him to see through his country’s plan to stop the flow of a key bomb ingredient across Pakistan’s border into Afghanistan.