The biggest game of the year officially launched at 12:01 a.m. at many retailers today, so we called up several stores to gauge whether or not supply is meeting demand.

Fortunately for retailers, GTA IV appears to be in good supply across the US’ East and Midwest regions, at least in the early afternoon on Tuesday.

But that could change fast once gamers clock out of their real-life jobs, and start to answer the siren call of Liberty City.

"It’ll be complete mayhem after work gets out," said a manager with independent Ind.-based retailer McVan’s Video Games. The chain currently has copies of GTA IV in stock, but the associate said unsurprisingly that it’s "guaranteed" to sell out by days-end on both PlayStation 3 and Xbox 360.

The big players are also stocked with GTA IV. A GameStop employee in Broadway Village, New York said that his store is not sold out of the game yet, adding that the Xbox 360 version is currently outselling the PS3 version.

Another employee at a GameStop in Manhattan Mall, New York said that the store is stocked with GTA IV, as did a GameStop staffer in Circle Centre, Indianapolis.

Many GameStop locations opened at midnight to sell the game to eager fans, while 24-hour stores like Meijer in the Midwest and Wal-Mart also began sales at midnight.

Talking to the various retailers--and this is just anecdotal--there isn’t one particular version that is vastly outselling the other.

"I’d say it’s a toss-up," said a worker at a Highland Park, Mich. Game Crazy, regarding the ratio of Xbox 360 to PS3 sales of the game. He added, "It’s not sold out yet, but will be by the end of the day."

An employee at a Chicago Game Crazy also said that the game was stocked, but the Xbox 360 version is outselling the PS3 version by "about 75 percent." She attributed the higher sales of the Xbox 360 version to the dowloadable content that will be available for that version of the game this fall.

General merchandisers like Target and "category killers" like Best Buy also had GTA IV available. "We’re selling [both versions] about equally, but maybe the PS3 version is selling a bit more," said an employee in the electronics department of a Dorchester, Mass. Target store.

Industry watchers have said they expect the game to generate $400 million in sales in the first week alone. Analysts have also said they expect the game to ship around 6 million copies in week one.

Analyst Michael Pachter with Wedbush Morgan forecast the game to ship 9 million units during the course of publisher Take-Two’s fiscal year, although Take-Two CEO Ben Feder told Reuters Monday that internal sales expectations are "higher than analysts give the game credit for."