As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT CREW REPORTED AFTER TAKEOFF, A LOUD EXPLOSION WAS HEARD AND SPARKS WERE SEEN COMING FROM THE NR 1 ENGINE. THE FLIGHT CREW DECARED AN EMERGENCY AND RETURNED TO DEPARTURE AND LANDED SAFELY WITHOUT FURTHER INCIDENT. AIRCRAFT GROUNDED. MAINTENANCE REPLACED THE NR 1 ENGINE AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK PER TASK CARD 26L40071004 AND 26L00071015.