A United Airlines plane was grounded Friday in Medford after it was found to be missing an external panel after it touched down on a flight from San Francisco.

The plane is a Boeing 737-824, according to Jackson County Airport Director Amber Judd. No injuries were reported, Judd said.

According to the aircraft’s N-number, the plane was delivered to Continental Airlines on Dec. 22, 1998. It has been operated by United Airlines since Nov. 30, 2011.

United Flight 433 landed safely, and the Medford airport was the scheduled destination, according to an email from United Airlines’ media relations team.

The flight was carrying 139 passengers and six crew.

“After the aircraft was parked at the gate, it was discovered to be missing an external panel,” United said in a statement. “We’ll conduct a thorough examination of the plane and perform all the needed repairs before it returns to service.”

“We’ll also conduct an investigation to better understand how this damage occurred,” the statement added.

There was no indication of the damage during the flight, according to United.

According to online flight trackers using the plane’s N- number, the aircraft had come to Medford from San Francisco. Earlier in the day it had flown from Nashville, Tennessee, to San Francisco. It was scheduled to fly to Denver later this afternoon.

Judd said the aircraft “will be here for a while,” indicating that the plane was not in condition to fly.

The location of the missing metal piece is unknown. “They don’t know where they lost it,” Judd said.

The search for the missing part prompted airport officials to temporarily close two runways. Judd said it lasted “just a matter of a few minutes, maybe 15 minutes” while crews ensured there was no debris.

“Then the other planes started landing and taking off,” Judd said.

An investigation is expected to be launched.