A teacher arrested when marijuana was found in her vehicle as she tried to cross from Mexico into the United States was released over the weekend after authorities confirmed that she was a victim of drug traffickers who use innocent people to smuggle drugs, officials said.

Ana Isela Martinez, who teaches English at an elementary school in El Paso, Texas, was released on Sunday.

Martinez was arrested on May 26 as she tried to cross one of the international bridges that span the Rio Grande and link Ciudad Juarez to El Paso.

Mexican authorities found 40 kilos (88 pounds) of marijuana in the trunk of Martinez's car and charged her with drug smuggling.

The teacher's family and friends staged a series of protests to demand her release from a jail in Juarez, considered Mexico's murder capital and the most violent city in the world in terms of homicides per 100,000 residents.

Martinez, who always claimed that she did not know where the drugs came from, was released on Sunday night after six weeks in jail and welcomed by about 100 people gathered outside the facility, prosecutors told Efe.

The teacher, who said goodbye personally to the warden and thanked him for the good treatment she received, emerged from the municipal jail accompanied by her husband, Isaac Cuanalo.

The couple plan to move to El Paso due to fears of retaliation by drug traffickers, Martinez said.

The federal Attorney General's Office dropped the charges against the teacher, who crosses the border daily to work and take her daughter to school in El Paso.

Investigators found evidence of "the operation of a gang of drug traffickers that uses unwitting people who cross the border frequently to smuggle without knowing that the drugs are in their vehicles," the AG's office said in a statement.

People who frequently cross from Mexico into the United States via the international bridges should "be alert and not allow their property to be used for illegal ends," the AG's office said.

Ciudad Juarez has three international bridges that connect it to El Paso.

One of the bridges, the one where Martinez was arrested, is equipped with the Secure Electronic Network for Travelers Rapid Inspection, or SENTRI, system, which lets people who have passed a background check receive a card for expedited crossings in designated lanes.

Participants in the trusted traveler program for frequent border crossers must apply with U.S. Customs and Border Protection, pass an FBI background check, undergo an interview with U.S. officials and pay an annual fee for their SENTRI cards.

Drug traffickers are apparently taking advantage of the looser security in the SENTRI lanes to smuggle drugs in the vehicles of unwitting drivers.

The Martinez case prompted authorities on both sides of the border to carry out surprise inspections of vehicles traveling in the SENTRI lanes, Efe confirmed.