A Qantas Airways flight made an emergency landing at San Francisco International Airport early Tuesday after an engine failure in midair punched a hole in the external casing, an incident that one expert called "extremely rare."

Qantas Flight 74, a Boeing 747 with 212 passengers on board, left San Francisco for Sydney about 11:30 p.m. Monday. The plane had reached 30,000 feet about 45 minutes after takeoff when a malfunction in the No. 4 engine on the right wing ripped a hole in the external casing, or cowling, authorities said.

Radar tracks on FlightAware, a flight-tracking website, show that the plane was about 275 miles west of San Francisco when the incident happened.

The pilot declared an emergency, made two wide circles over the Pacific to dump fuel to reduce the plane's weight and returned to SFO at 12:45 a.m., authorities said. Airport fire trucks surrounded the plane as it arrived.

No one was injured, and the passengers were "put up in hotels for the night," said SFO duty manager Chris Davison.

The cause of the engine failure will be investigated by Australian aviation safety officials, and any findings will be reviewed by the Federal Aviation Administration and the National Transportation Safety Board.

Records show that the plane was delivered to Qantas in 1992.

Boeing 747s have four engines and "are designed to actually lose three of four engines and still be able to get back," said pilot and aviation consultant John Nance.

Engines can fail if a foreign object such as a bird is pulled in, or if a part such as a blade comes apart.

Failures are often contained within the engine, but what happened on the Qantas jet is known as an uncontained failure because a piece of the engine pierced the cowling at high speed, Nance said.

This kind of failure is "an extremely rare event," he said.