B737 Next Generation Undifferentiated
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 117; Flight Crew Total 18000; Flight Crew Type 1280
Troubleshooting
Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition; Flight Crew Diverted
Aircraft
While in cruise flight at FL340; a flight attendant called and asked for the main cabin to be cooled down. I noticed that the cabin duct temperature had gotten to 25 degrees C. I turned the passenger cabin temperature to cooler. Not long after that the flight attendant calls back and says she sees and smells smoke around the exit row that filled the ceiling. The passengers noted this as well. She described it as a fine mist that smelled like electrical wires burning. The Captain then went back to investigate. He could also smell the burning smell but the smoke had dissipated. After he returned to the cockpit we discussed returning to ZZZ or going to ZZZ1. We decided to do a bit of troubleshooting to be able to give maintenance more information when we landed. Since we had been using the engine anti ice during climb we wondered if the smell had come from that system. The Captain then went back into the cabin and gave a signal to the flight attendant for me to turn the anti-ice back on so he could observe whether there was any more smoke or smell. He did notice some additional smoke and burning smell. After he returned to the cockpit he [notified ATC] and coordinated with Dispatch to divert to ZZZ1. We requested that the fire trucks be waiting for us. We landed in ZZZ1 about 25 minutes later with no incident.
Leveling off at FL340 a F/A (Flight Attendant) called to ask us to cool off the cabin. The FO (First Officer) changed the temp to cooler. Soon after the preservation called the flight deck saying that she sees and smells smoke near the emergency exits. She said that it was a fine mist. I set up the blocking and went to investigate. I could not see smoke or mist but noticed a very faint unidentifiable odor then it was gone. I returned to the flight deck to discuss diversion options with the FO. I received a 2nd call front the purser saying that the odor has returned. I again set up blocking [flight deck door] to investigate. I had a FA call the flight deck to have the FO turn off and on the engine anti ice. I noticed a very faint odor. A FA in the rear galley signaled me to come there. She told me to look at the cabin overhead lights. There I could barely see a mist. I returned to the flight deck; [notified ATC] and diverted to ZZZ1. I requested fire department assistance. We landed normally without further incident.
B737 NG flight crew reported Flight Attendant notification of cabin electrical fumes and associated smoke in passenger cabin. After troubleshooting with no results; aircraft executed an uneventful diversion.