SAO PAULO (Reuters) - Thieves broke into Sao Paulo's leading art museum before dawn on Thursday and stole two oil paintings, including one by Pablo Picasso that could be worth some $50 million.
Picasso's 1904 "Portrait of Suzanne Bloch" -- from the Spaniard's Blue Period -- and Brazilian painter Candido Portinari's 1939 "The Coffee Worker" were among the Art Museum of Sao Paulo's most important exhibits, the museum said in a statement.
The thieves probably specifically targeted the paintings, which were on display in separate rooms on the second floor, it said.
"We believe that this has the hand of some collector, for his private use," Marcos de Moura, who is heading the police investigation, told a news conference. "This was a professional job, nothing amateur."
Three thieves broke through the main door of the museum just after 5 a.m., then smashed another glass door while an accomplice kept watch outside, de Moura said. They spent only three minutes inside the building.
There was no alarm on either door. Security cameras filmed the break-in but not the exact moment when the paintings were lifted from the walls, he said.
None of the thieves wore a hood, he added.
The museum said it would be closed for the next few days and asked Brazil's Foreign Ministry and the international police agency Interpol for help.
Museum officials and police declined to say how much the paintings might be worth.
But Globo news quoted art expert Jones Bergamin as saying the Picasso could be worth as much as $50 million. He valued the Portinari at about $5.5 million.
In October two thieves tried to break into the museum but were spotted and fled.
Its collection is considered the most important in Latin America, featuring works from European masters including Velazquez as well as modern artists such as Dali and many Brazilians.
Reporting by Mauricio Savarese; Writing by Angus MacSwan; Editing by Xavier Briand