Google unveiled its first tablet at the annual I/O conference last month and said that the Nexus 7 tablet will hit store mid-July. Fulfilling the promise, Google has started shipping the much awaited Android tablet, but still there is no specific date about when the tablet will be available for in-house purchases at retail stores countrywide.

The company confirmed in a Google+ post on Friday that it has started shipping Nexus 7 preorders. Google also confirmed the same on its Google Nexus Twitter page.

Google is taking orders for the Nexus 7 tablet and promising delivery within two weeks. The 8GB model of Nexus 7 is priced at $199 on the Play Store, while the 16GB model costs $249.

"We're now shipping Nexus 7 pre-orders. The first wave of orders are going out today and all ore-orders are scheduled to ship within next 3 business days. Once your order has shipped you will received a confirmation email and tracking number. Though our agents are unable to provide a specific delivery date for individual pre-orders, please rest assured that our shipping team is working to fulfill all orders as quickly as possible," said an automated message on Google help line, according to Android Police.

Nexus 7 preorders shipments arrived on U.S. retailers on Friday, but most of the retailers sold out all the units that were shipped to them and are waiting for newer shipments to arrive.

GameStop U.S. sent out confirmations on Friday that customer can pick up their Nexus 7 pre-orders, but the retailer pulled out Nexus 7 orders page from its Web site after a while. Staples U.S. also sold out all the shipments and said that they are waiting for additional shipments to arrive. Staples recommends users to check in between July 14 to July 18 as newer units may arrive that time. The scenario is same across Wal-Mart, Sam's Club and Andorama.

According to GameStop, the second wave of Nexus 7 shipments can take few weeks to arrive. Some other retailers are also taking up preorders, but highlight August delivery for the Nexus 7 tablet.

In Canada, GameStop and Futureshop expect the tablet to reach its inventory on Aug. 10.