Narrative:

In cruise at fl 360; relatively smooth with occasional light turbulence. About 50 mi south of ZZZ. Forward and aft lower cargo compartments indicated fire with associated EICAS; master warning; and aural alert. Called for QRH procedure and executed an immediate turn and descent toward ZZZ while simultaneously [advising ATC]. Pm (pilot monitoring) found appropriate QRH checklist and began execution. Just prior to fire bottle arming step; all alerts and warning cease on their own. We discussed and considered the likelihood that both compartments had independently caught fire and extinguished on their own simultaneously and agreed that it was very likely a malfunction. We elected not to arm or discharge the fire bottle(s) as the situation no longer conformed to the QRH condition statements and our reasoning that there was a malfunction. We did; however; elect to continue to ZZZ. Upon landing on runway xx; we immediately shut down the right engine while establishing communication with crash/fire rescue and asked them to conduct thermal imaging assessment of the forward and aft lower cargo compartments. Both were reported as cold. We taxied to the ramp.upon arrival a ZZZ; ramp personnel opened the lower cargo compartments. Ramp and maintenance both reported that they had been loaded in excess of the compartment's marked limits. From the mx write-up resolution 'upon arrival at ZZZ; it was noted that the fwd and aft cargo compartments were loaded with bulk freight all the way to the ceilings'. All system tests were normal and our best guess is that improper compartment loading led to the erroneous fire indications. No obvious equipment deficiencies were found.suggestions: retraining and refreshing of ramp personnel regarding the importance of proper loading procedures and compliance with limitations. It may be instructive to inform them of the consequences of failure to comply with procedures. Also of note/concern was the fact that ZZZ ATC did not have any contact information for [company] operations. Because of the time critical nature of the incident; we were not able to communicate directly with the company [ramp or operations]; and ATC did not have the information to do so. I suspect that is an item that needs refreshing at more than just this one station.

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Original NASA ASRS Text

Title: B757 flight crew reported diverting due to a Cargo Fire EICAS Master Warning.

Narrative: In cruise at FL 360; relatively smooth with occasional light turbulence. About 50 mi south of ZZZ. Forward and aft lower cargo compartments indicated fire with associated EICAS; Master Warning; and aural alert. Called for QRH procedure and executed an immediate turn and descent toward ZZZ while simultaneously [advising ATC]. PM (Pilot Monitoring) found appropriate QRH checklist and began execution. Just prior to fire bottle arming step; all alerts and warning cease on their own. We discussed and considered the likelihood that both compartments had independently caught fire and extinguished on their own simultaneously and agreed that it was very likely a malfunction. We elected not to arm or discharge the fire bottle(s) as the situation no longer conformed to the QRH condition statements and our reasoning that there was a malfunction. We did; however; elect to continue to ZZZ. Upon landing on Runway XX; we immediately shut down the right engine while establishing communication with crash/fire rescue and asked them to conduct thermal imaging assessment of the forward and aft lower cargo compartments. Both were reported as cold. We taxied to the ramp.Upon arrival a ZZZ; ramp personnel opened the lower cargo compartments. Ramp and maintenance both reported that they had been loaded in excess of the compartment's marked limits. From the MX write-up resolution 'Upon arrival at ZZZ; it was noted that the FWD and AFT cargo compartments were loaded with bulk freight all the way to the ceilings'. All system tests were normal and our best guess is that improper compartment loading led to the erroneous fire indications. No obvious equipment deficiencies were found.Suggestions: Retraining and refreshing of ramp personnel regarding the importance of proper loading procedures and compliance with limitations. It may be instructive to inform them of the consequences of failure to comply with procedures. Also of note/concern was the fact that ZZZ ATC did not have any contact information for [company] operations. Because of the time critical nature of the incident; we were not able to communicate directly with the company [Ramp or Operations]; and ATC did not have the information to do so. I suspect that is an item that needs refreshing at more than just this one station.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.