Feb 16 (Reuters) - The United States is looking into reports that Egypt has detained relatives of prominent Egyptian-American human rights activist Mohamed Soltan, U.S. State Department spokesman Ned Price said on Tuesday. "We have and we continue to engage the Egyptian government on human rights concerns, and we take seriously all allegations of arbitrary arrest or detention," Price told a news briefing. Soltan's organization, The Freedom Initiative, in a statement said six members of his family were detained on Sunday by plain-clothed Egyptian State Security forces as part of a "campaign of retaliatory aggression." Soltan "is calling attention to the impunity and disregard for human rights under the current Egyptian regime. Now the Egyptian regime is arresting his relatives to try to intimidate him into silence," his lawyer Eric Lewis said, according to the group's statement.