Theives who made off with six paintings from South Africa's Pretoria Art Museum 'mistakenly' abandoned the priciest art work in their haul.

The City of Tshwane / AP Photo This undated photo provided by The City of Tshwane on Monday, Nov. 12, 2012, shows a 1931 Irma Stern "Fishing Boats" oil on canvas. Police in South Africa said Monday that robbers posing as visitors to an art museum stole more than $2 million worth of art including "fishing boats" from an exhibit near the country's capital.

If you’re going to carry out a major art heist, perhaps you should do a little research first. That’s presumably what the thieves who robbed South Africa’s Pretoria Art Museum learned on Sunday. Although the burglars successfully stole five paintings worth more than $2 million collectively, they ditched a sixth piece that would have been the most valuable in their pilfered collection, ABC News reported.

When the three criminals discovered that one painting was too large to fit in their getaway car, a Toyota Avanza, they dropped it on the ground and sped off without it, according to the Los Angeles Times. Unfortunately for them, the abandoned piece was “Two Malay Musicians” by Irma Stern—a famous work worth around $1.5 million.

The robbers entered the museum, which houses some of South Africa’s most treasured art, paid the admission fee and pretended to be an art lecturer and two students. Then, they pulled out guns and a list of works they forced an employee to find. They fled with five paintings by such prominent South African artists as Gerard Sekoto and J.H. Pierneef, as well as with another painting by Stern, the Los Angeles Times reported.

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“All the artists they took are artists who are doing brilliantly in South Africa and internationally,” Imre Lamprecht, head of the art department at South African art auction house Stephan Welz & Co., told ABC. “These works are some of the best works they would have produced.”

Although Lamprecht was horrified to learn of the raid, she said the tossing of “Two Malay Musicians” was undoubtedly a mistake on the part of the burglars, ABC reported.

“Obviously these thieves didn’t know anything about art because that is not the painting whoever hired them would want them to leave behind,” Lamprecht said.

Stern is the museum’s most famous artist, Lamprecht said; her expressionist work “Arab Priest” sold for close to $5 million last year.

The burglary has called attention to security problems in South Africa’s public museums, which often have outdated systems and no guards, ABC News reported. At the time of Pretoria’s robbery, the museum’s closed-circuit television security system was broken, but three private security guards were keeping watch over the collection, the Los Angeles Times noted.

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According to the Associated Press, South African authorities are still investigating the burglary at Pretoria.

“I hope the government learns a lesson and puts in security structures that keep our art and heritage safe,” Lamprecht reportedly said.

Indeed, the Los Angeles Times found that several other critics have taken Pretoria’s misfortune as an opportunity to air their long-standing grievances. Johan Welmans, a spokesman for South Africa’s Democratic Alliance party, said he has been vocal about the museum’s security flaws.

“I have alerted the Tshwane metro about the lack of commitment toward this institution for a long time. The impression I got is that the Pretoria Art Museum is simply not a priority for the ANC-led Tshwane metro,” he said in a statement quoted by the L.A. Times.

Pieter de Necker, a spokesman for the Twashne mayor, reportedly told the South African Press Association that several other museums across the country have similar safety worries. According to the Associated Press, de Necker said art thefts remain uncommon, but he has recently noticed that South African works have become more prized in the international art market.

Although unusual, this is not South Africa’s first experience with museum heists. The AP noted that four limited-edition prints by artist William Kentridge were stolen from a Johannesburg gallery in February 2011, and bronze statues have been targeted in other South African museums.

Using statistics from Interpol and the FBI, the AP reported that art theft is the third most lucrative crime in the world, beat out only by drugs and illicit arms sales. The Pretoria heist, however, would have been more profitable for the robbers if they had maybe just taken a moment to prioritize.

Update: BBC News has reported that four of the five stolen paintings have been recovered. Police found the pieces under a bench at a local cemetery, but are still looking for the fifth painting by Gerard Sekoto. No arrests have been made.

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