TULSA, Okla. (AP) _ About 20 National Guardsmen from Tulsa will be the first Oklahoma troops participating in a mission to help prevent illegal immigration along the Mexican border.

Troops from the 138th Civil Engineering Squadron will depart on commercial flights to California throughout the day Saturday, beginning about 6 AM, Col. Pat Scully said.

The troops are expected to stay about three weeks. Scully wasn't sure about their exact duties in assisting the U.S. Customs and Border Patrol and California National Guard.

President Bush announced in May a plan that calls for sending up to 6,000 National Guard troops to the border to help with immigration enforcement. Gov. Brad Henry said a week ago that Oklahoma would participate in that effort.

More than 300 Oklahoma troops are to take part in the mission during the next three months.