Federal agents investigating the activities of Jeffrey Thompson, a major city contractor and a prolific contributor to political campaigns in the District, seized more than 23 million electronic pages of records when they raided his home and offices in March, court records show.

Although federal prosecutors have been mum about their probe of Thompson, U.S. District Judge Royce Lamberth revealed details of the searches in an opinion issued last month. The Legal Times first reported the ruling Monday.