(AP) — Federal aviation regulators are ordering United Airlines to step up inspections of all Boeing 777s equipped with the type of engine that suffered a catastrophic failure over Denver Saturday.

United says it is temporarily removing those aircraft from service. Boeing has recommended aircraft with the engines be grounded pending a decision on inspections.

The announcements came a day after United Airlines Flight 328 had to make an emergency landing at Denver International Airport after its right engine blew apart just after takeoff.

The National Transportation Safety Board said two of the engine’s fan blades were fractured although it did caution that it was too early to draw conclusions about how the incident happened.