On 20 February 2009, a group of men in a pickup truck threw explosive devices at the installations of the Secretariat of Public Safety of the municipality of Zihuatanejo, resulting in five persons injured. The attack occurred at 7:45 pm near the municipal docks. At the time of the attack, the 56th Infantry Battalion had been stationed in Zihuatanejo, mostly to interdict the traffic in arms, drugs and stolen vehicles. The grenade attack on the security headquarters was followed by a highway ambush that killed four policemen. Kidnapping of Mexican citizens has been a problem here as well. In one instance four kidnapping victims were rescued by elements of the Mexican military and police, killing one suspect in the process.