WASHINGTON — The United States Army Corps of Engineers has begun preliminary preparations for the construction of segments of a wall in several places along the border with Mexico, the Department of Homeland Security said on Tuesday.

Engineers are drilling and taking soil samples to determine what type of barriers would be most effective in the different types of geography along the border, said David Lapan, a spokesman for the Department of Homeland Security.

The drilling and soil testing are taking place in El Paso; Santa Teresa, N.M.; Calexico, Calif.; and the Rio Grande Valley in South Texas. Mr. Lapan said the testing has been completed in El Paso and Calexico. The agency has identified the San Diego area and the Rio Grande Valley as priority regions for new border walls. The Corps will begin work in the San Diego area in August.

The drilling and testing come as Customs and Border Protection, the parent agency of the Border Patrol, continues to evaluate dozens of proposals that have been submitted by vendors for designs for a border wall.