The recorders were sent to the National Transportation Safety Board's lab in Washington for analysis on Tuesday. The plane was also slowly towed off the runway.
Cellphone video taken onboard Southwest Flight 345 captured the hard landing on Monday. Sparks were flying as the Boeing 737 slid more than 2,175 feet before coming to a screeching halt.
Officials said 10 passengers were treated at the scene, and six were taken to a hospital with minor injuries. Southwest said 150 people were on the flight, while the Port Authority of New York and New Jersey said the total was 149. The passengers exited the plane by using chutes. They were put on a bus and taken to the terminal.
Aviation expert Michael Barr said he's positive Flight 345 had a mechanical problem.
"The reason for that is that the pilot at no time during his approach had any unsafe gear indications inside the airplane," said Barr.
In September 2005, a JetBlue flight leaving Burbank also experienced a nose gear issue on its way to New York. But that plane let the pilot know there was a problem. So Flight 292 was able to circle Los Angeles for three hours crippled by faulty landing gear, dumping jet fuel on the way.
The broken landing gear burst into flames as it hit the runway when the pilot cautiously brought the plane down. The Southwest pilots and passengers didn't get that opportunity.
Thee Associated Press contributed to this report.