Thieves broke into the Sao Paulo Museum of Art and made off with paintings by Pablo Picasso and Candido Portinari in a brazen heist Thursday morning that lasted just three minutes as recorded by security cameras.

They stole Picasso's "Portrait of Suzanne Bloch," which he painted in 1904 during his Blue Period and is among the most valuable pieces in the museum's collection, said museum spokesman Eduardo Cosomano.

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They also took "O Lavrador de Cafe" by Portinari, a major Brazilian artist.

The thieves used a hydraulic car jack to pry their way past the pull-down metal gate that protects the museum's front entrance. Then, they smashed through two glass doors, probably using a crow bar, to get to the paintings on the second floor, police said.

"This is a highly professional job, done by people who knew exactly what they were doing," said the lead Sao Paulo police investigator on the case, Marcos Gomes de Moura.

"Everything indicates they were sent to do it by some wealthy art lover for his own collection — someone who, although wealthy, was not rich enough to buy the paintings," Moura added.

Sao Paulo police have sent alerts out to try to stop the paintings from leaving Brazil, Moura said. And while he doubts the paintings are being held for ransom, he said police are ruling nothing out.

Security cameras captured video images of three men entering the museum but little else, and the images are of very poor quality, he said.

Police believe there may have been a fourth person acting as a lookout because they found headphones outside the museum, a modern slab-like structure suspended over Sao Paulo's main avenue.

The two paintings were hung a good distance from one and other — another reason Moura believes the thieves were highly professional.

Thieves attempted a robbery at the same museum in late October but were foiled by the alarm system. This time, the museum's main alarms failed to go off, and the room from where the two paintings were stolen, frames and all, had no alarm, he said.

The robbery took place shortly after five in the morning, just when guards were changing shifts.

Police were interviewing 30 museum employees in connection with the crime but Moura said all of the guards were longtime employees, none with less than 10 years on the job.

Moura would not speculate on what the paintings may be worth.

Local media reports estimated their value at around $100 million, but Cosomano and other curators said it is difficult to put a price on them because the paintings had not gone to auction.

"The prices paid for such works would be incalculable, enough to give you vertigo," said curator Miriam Alzuri of the Bellas Artes Museum of Bilbao, Spain.

"O Lavrador de Cafe," which depicts a coffee picker, was painted in 1939 and is one of the most renowned works by one of Brazil's most famous painters. Portinari (1903-1962) was an influential practitioner of the "neo-realism" style. His most famous works outside Brazil are the "War and Peace" panels at the United Nations building in New York.