A Maryland law firm and three of its lawyers are accused in a civil suit in Washington, D.C., of failing to return a nearly $1.6 million federal tax refund to the Nigerian embassy following the sale of property in the capital.

The embassy of the Federal Republic of Nigeria, represented by Patton Boggs, sued ECU Law Group of Silver Spring, Md., this week in U.S. District Court for the District of Columbia. The suit alleges the attorney who handled the real estate transaction for the embassy hasn’t returned a $1.55 million IRS tax refund to Nigeria.