22 bodies buried in a mass grave were found by Iraqi soldiers near the Lake Tharthar northwest of Baghdad.
The bodies were found Saturday during a joint operation with U.S. forces, the military said in a statement.
Last month, Iraqi police reported finding 25 bullet-riddled bodies, some decapitated, in a mass grave in Nadhum village, close to Lake Tharthar. At the time, police said it appeared the victims had died within the past three months.
But an Anbar provincial police official, Col. Jubair Rashid Naief, said Tuesday that he believed these were not the same bodies, and that this was a second mass grave found in the area in less than a month.
Naief said the bodies were found in a drainage canal, and that some of the victims were wearing heavy clothes - indicating they may have been killed last winter.
After the discovery, U.S. and Iraqi forces launched an operation Sunday, including ground raids and air assaults targeting al-Qaida in the area, the U.S. statement said.
About 30 suspects were detained, it said. Two car bomb facilities and a number of weapons caches were also found, it added.
Iraqi officials are investigating the mass grave, trying to identify the bodies and notify families. The statement did not say how long the victims were believed to have been dead.