As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DSM - FLT 558 - IN ICE ABOVE 26,000 FEET, ALL 4 ENGINES ROLLED BACK TO 40-45 PERCENT. CREW SHUT DOWN NR 1 AND NR 2 DUE TO RISING TGT (APPROXIMATELY 900 DEGREES CELSIUS). NR 2 WAS RE-STARTED. NR 2, NR 3, AND NR 4 RECOVERED. LANDED WITHOUT INCIDENT DSM. MAINTENANCE TO CHARTER THE A/C IN AM.