McALLEN, Texas (AP) — Federal agents arrested 30 alleged members and associates of a prison gang Thursday on charges that they worked with Mexican organized crime to bring drugs into the U.S. in South Texas and distribute them north.

Thursday's sweep was the result of a four-year investigation by the DEA and FBI into the notorious Mexican Mafia prison gang and its drug trafficking, said U.S. Drug Enforcement Administration Special Agent in Charge Javier Pena. The gang has close ties with the Zetas cartel, which maintains a stronghold in Nuevo Laredo, Mexico across the Rio Grande from Texas.

For years, Mexican drug trafficking organizations have used U.S.-based prison gangs to handle some of their enforcement activities, as well as their U.S. drug distribution. The gangs are generally run by leaders who are behind bars, but they maintain an extensive network of members on the outside.

The Mexican Mafia allegedly brought drugs across the border at Laredo and moved them up through San Antonio, Austin and Fort Worth. One of those arrested Thursday was the alleged Mexican Mafia captain who oversaw the gang's activities in Laredo, Pena said.

"We will not tolerate any type of gang activity or organized crime," Pena said from Laredo. "If they are working an area we're going to target them."

Some of those arrested were already in custody, but most were out on the street. The agencies had targeted 34 people in total and were looking for the remaining four.

Most of the arrests were made around 5 a.m. Thursday in Laredo, with a couple of additional ones coming in San Antonio and Austin. Local authorities and agents with the U.S. Immigration and Customs Enforcement and Border Patrol assisted in the arrests.

The alleged gang members were expected to make their initial appearances in federal court Friday. They will face charges of possessing and distributing marijuana, cocaine, heroin and methamphetamine.