As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FOR FLIGHT 4309 WHILE STILL AT THE GATE THE CREW REPORTED THAT AFTER TURNING THE PACKS ON FOR 5 MINUTES, NOTICED A BURNING SMELL IN THE CABIN AND HAZE. THE AIRCRAFT WAS REMOVED FROM SERVICE. FOUND 2 FLUORESCENT LIGHTS GOING OUT AT SEATS 9 AND 10. REMOVED AND REPLACED THE LIGHT BULBS IAW CRJ 700 AMM 33-21-06. NO DEFECTS NOTED. THE AIRCRAFT WAS RETURNED TO SERVICE.