A military spokesman, Brigadier Qassim al-Moussawi, said the poisoning probably was intentional, though he did not rule out that spoiled food could have been used in the meal by contractors or officers to skim off money from food funds.
The policemen fell ill after eating their iftar, the meal that ends the sunrise-to-sunset fast during the Islamic holy month, at their base in the southern town of Numaniyah.
Also detained for questioning was the Iraqi contractor hired to provide food for the base and a number of other people, Moussawi said, without providing details.
Baghdad was torn by new violence. A car bomb ripped through a market in a Shi'ite district, killing at least 10 people and wounding 23 -- an attack possibly carried out by Sunni insurgents.
Gunmen also kidnapped 11 policemen in a brazen assault on their checkpoint in Sadr City, a Baghdad neighborhood dominated by the Mahdi Army, the country's most powerful Shi'ite militia.
Elsewhere in Iraq, the US military announced that three Marines died Sunday after fighting in the western region of Anbar, a hotbed of Sunni insurgents, bringing to 32 the number of American service members who have died in Iraq this month.
The death of the brother of Vice President Tariq al-Hashimi, the country's most prominent Sunni Arab politician, alarmed Sunnis and fueled their demands that the government crack down on Shi'ite militias.
Critics of Prime Minister Nouri al-Maliki accuse the Shi'ite leader of hesitating on reining in the militias, because many of them, like the Mahdi Army, belong to parties in his government.
``The clock is starting to strike after today's events," Khalaf al-Alayan, a Sunni parliament member said. ``They [Shi'ite militias] consider Sunnis terrorists who must be killed. If the zero hour is coming, we will take the decisions needed to defend ourselves."
``We say to the government, you still did not disarm the militias," Salim Abdullah Tawfiq, a Sunni politician, said in a statement read in parliament. ``And here is what it has led to."
Maliki condemned yesterday's killing as an ``ugly, terrorist crime."
