U.S. Transportation Secretary Anthony Foxx has stepped up his pressure on Washington's subway system by replacing three Metro board members and telling officials there would be "no more excuses" regarding continued safety problems.

Foxx announced the appointments of three new federal Metro Board members in a Thursday statement.

Foxx says he has been frustrated by the 16-member board's delay in creating a new safety oversight office.

The new members are former National Transportation Safety Board Vice Chairman Carol Carmody, former National Highway Traffic Safety Administration administrator David Strickland and Federal Railroad Administration Chief Safety Officer Robert Lauby.

Former Board Chair Mort Downey, planner Harriet Tregoning, and engineer Anthony Giancola are being replaced.

The subway system was shut down for 29 hours last month for a system-wide inspection after an electrical fire.