Topeka ? An additional 900 soldiers at Fort Riley have received orders this week to prepare to move out as part of the military buildup in the Middle East, post officials said Wednesday.

The soldiers are part of the 3rd Brigade, 1st Armored Division and the 937th Engineer Group, based at Fort Riley. It’s the second significant deployment for the units in recent weeks.

Earlier this month, 1,500 active duty soldiers with the 3rd Brigade, 1st Armored Division and 937th Engineer Group were ordered to deploy to support Central Command, which is based in Tampa, Fla., and has control of activity in the Persian Gulf.

The United States has been building up its military presence in the region for possible war against Iraq.

Fort Riley spokeswoman Christie Vanover said she could not disclose the soldiers’ mission or departure times for security reasons. The post is home to more than 10,000 soldiers.

“Really, about a third of the post will be gone in the near future,” Vanover said.

Vanover said a group from the initial 1,500 soldiers ordered to deploy left Tuesday night.

In addition, between 400 and 500 soldiers with the 1st Brigade, 1st Infantry will soon deploy for scheduled exercises in South Korea. Vanover said the deployment was scheduled before the recent tensions between the United States and North Korea about nuclear weapons.

She also said that 300 Reserve and National Guard soldiers had been ordered to mobilize at Fort Riley and prepare for deployment in support of global war on terrorism.