There was a report on the local news over the weekend about this incident.
Air to ground communications was compromised by an illegal FM radio station transmiting a very powerful signal on a frequency around 100MHz in the Guarulhos area. This site has since been closed down and the equipment confiscated by the authorities.
It was also reported that the pilots did not have the relevant NOTAMS concerning the work in progress at GRU.
As usual, there wasn't just one factor involved in the incident.
Tchau