Deputy Prime Minister Bulent Arinc declined to call the blast a terrorist attack, adding that an investigation was still ongoing, CNN reported.
"In situations like this all possibilities are considered," Arinc said.
He said the minivan was traveling from Syria to Turkey when it exploded at a busy Turkish customs gate.
The blast was so powerful a man who lived more than a mile away from the gate told CNN he heard it.
Separately, rebels opposed to Syrian President Bashar Assad captured a military air base in northern Syrian just one day after seizing control of the country's largest hydroelectric dam at al-Tabaqa, Voice of America reported.
The British-based Syrian Observatory for Human Rights said the rebels took over the al-Jarrah air base in Aleppo province.
At least 60,000 people have been killed since the Syrian conflict began, the United Nations has said.
U.N. Secretary-General Ban Ki-moon told the Council on Foreign Relations in New York Syria is "self-destructing."