Motorola Mobility said that the Chinese authorities have extended the second phase of an investigation into its proposed acquisition by Google.

In a regulatory filing, it was noted that the companies “continue to work closely with Mofcom to conclude its investigation and expect the transaction to close during the first half of 2012.”

Clearance from the Chinese authorities marks the final hurdle for the US$12.5 billion deal, which has been investigated and cleared without conditions in all other markets where required.

The deal is being probed by the Anti-Monopoly Bureau of the Ministry of Commerce of the People’s Republic of China.

Motorola picked up clearance for the deal from the EU and the US Department of Justice in February 2012, after in-depth reviews related to the impact on competition and the possible future uses of Motorola’s patent portfolio.

The companies first announced their combination in August 2011. At this point, it was stated that the deal was expected to close “around the end” of that year.