RIO DE JANEIRO, Jun. 5 -- Only one week before the beginning of the FIFA World Cup, Brazil's largest city Sao Paulo faced major traffic problems due to a subway workers' strike on Thursday.

Several of the subway lines were not operational, which caused citizens to resort to the railway system, buses and cars, leading to huge traffic jams - according to daily O Globo, morning traffic was the third slowest on history - and thousands of citizens not being able to get to work in the morning.

It is not the first time Sao Paulo faces transportation problems: bus drivers went on strike for two days in May and passengers were left without a lot of options then, as the subway and railway lines do not cover the entire city and are not sufficient to deal with the extra number of passengers.

Sao Paulo will host the World Cup's opening match, Brazil versus Croatia, on June 12th, as well as other five matches, including a semifinal. Most of the match goers are expected to get to the stadium by public transport, including the five subway lines in the city.