Army investigators yesterday discovered three aluminum boxes -- each holding $4 million in $100 bills -- that they believe the sticky-fingered soldiers stashed away to be recovered by them at a later time when the coast was clear, sources said.

The boxes were found tucked away by a bank of the Tigris River near a walled-up cottage, inside of which the soldiers and other members of their unit Friday said they found 37 aluminum boxes, each containing $4 million, the sources said.

Officials believe there were actually 40 boxes -- and that the three soldiers improperly removed the three boxes with $12 million from the cottage and hid them by the river bank. Another $200,000 may still be missing, the sources said.

The Post reported yesterday that four GIs, three engineers and a driver, are facing courts-martial for swiping $900,000 from Saddam Hussein's booty.

The engineers are accused of stashing $600,000 in a tree, while the driver is accused of hiding $300,000 in a bag, a cooler and a glove box in his cargo truck.

Friday, soldiers of the 4th Battalion of the 64th Army Division stumbled upon $700 million in cash in cottages that had been walled up with cinder blocks on estates in the palace district, where senior Ba'ath Party and Republican Guard officials lived.

Yesterday, as searches continued, an additional $112 million was found in another cottage in the neighborhood -- bringing the total stash to $824 million, including the $12 million found by the river.

As a result of the arrests, the district is now swarming with members of the Army's Criminal Investigation Division.

The Pentagon and Central Command had no comment on the arrests, which were confirmed to The Post by Maj. Kent Rideout, a top commander on the scene. The names of those arrested were not released.

Soldiers of the 64th Division -- men who fought in the fiercest battles of the war and are now bearing the brunt of securing and policing Baghdad -- aren't happy about the searches for the missing money.

They complain about how quickly Central Command brought in planes to take out the cash and bring in the "narcs" -- as they derisively call the CID -- "when it takes so long to get mail, parts and interpreters up here," according to one GI.

Many soldiers also told The Post that they believe some of the found millions should have been used to give a "bonus" to the troops who won this war.

Failing that, they say, it should help pay for the war and the costs of policing occupied Iraq.