(CNN) -

A Guam-bound United Airlines flight that was forced to land on remote Midway Island after pilots detected an electrical odor experienced a mechanical problem, the carrier said Monday.

The Boeing 777 was carrying 335 passengers and 13 crew from Honolulu when it diverted to the Pacific atoll last Thursday, United spokeswoman Mary Clark said.

Another plane returned the passengers to Hawaii on Friday after seven hours on the island, and they made it to Guam the next day, she said.

United blamed the diversion on a cooling fan problem, which mechanics fixed, Clark said. It has returned to service.