RIO DE JANEIRO, Feb. 20 (Xinhua) -- The Brazilian police on Tuesday arrested at least 40 people in two large operations against child pornography in Sao Paulo, official sources said.

All the arrests were made after police had seized their computer and found pornographic material involving minors. An assortment of toys was also seized.

One of the operations was in Taboao da Serra, a town in the metropolitan region in Sao Paulo.

The investigation began six months ago, when the police received an anonymous tip-off, and led to the arrest of at least 28 people on Tuesday morning.

The other operation happened in Sao Paulo itself, with 29 search and arrest warrants and with at least 12 people being arrested.

The police tracked the suspects by investigating computers which were regularly used to access child pornography.

Police spokesperson Marcio Fruet said "one of our suspects worked in a playground. Therefore, he had contact with children. Another suspect worked in a kindergarten."

"Therefore, these suspects will be watched with greater caution ...(to see) if they also produced and practiced this violence against children themselves," Fruet added.