WASHINGTON  The Obama administration said Tuesday that it would move hundreds of federal agents to the country’s southern border to prevent a spillover of drug-related violence from Mexico, and that it would focus more efforts on stopping weapons and money from flowing south.

In a briefing with reporters on Tuesday, the secretary of homeland security, Janet Napolitano, said that 360 agents would be sent to the Border Patrol and to Immigration and Customs Enforcement units along the 2,000-mile border, and that 100 agents would be sent to Bureau of Alcohol, Tobacco, Firearms and Explosives units there.

Officials said 100 of the redeployed Border Patrol agents, and several new canine teams, would inspect people and vehicles leaving the United States, aided by mobile X-ray units for cars and more sophisticated license-plate readers.

Ms. Napolitano called the redeployment “a very robust movement of personnel.” She added, “If anything, this is really the first wave of things that will be happening.”