Dozens of people believed to be among North County’s biggest criminal gun and drug dealers were arrested in a massive takedown Wednesday that federal prosecutors said had dealt a significant blow to the area’s heroin supply.

A total of 55 men and women have been charged in 10 federal indictments that accuse them of heroin and methamphetamine trafficking, along with illegal gun possession, money laundering, robbery, theft, assault and burglary.

The arrests were announced Wednesday afternoon at a news conference at the Oceanside Police Department. By midday, 46 of the 55 defendants were in custody.

“Today’s actions are our most significant law enforcement answer to date to the heroin epidemic that is facing our community,” said Acting U.S. Attorney Alana Robinson, who was joined by officials from the FBI, Sheriff’s Department and Oceanside Police Department.

The yearlong investigation involved wiretaps, surveillance and undercover buys.

Robinson said many of the defendants in the case are connected to a drug trafficking organization operating out of Tijuana that used San Diego County gang members as distributors.

The organization, linked to the Sinaloa cartel, reportedly supplied at least 25 percent of the heroin sold and consumed in North County.

“With these indictments we are taking over 20 alleged distributors off the streets, dealers who moved over a kilo of heroin a month for at least the past year, until today,” Robinson said. “That’s a huge blow to the heroin supply in this region.”

More than 150 law enforcement officers, led by the North County Regional Gang Task Force, swept through the region early Wednesday and arrested 14 people. Thirty-two others were arrested earlier in the week or were already in custody.

Eight defendants remain at large, including two believed to be in Mexico. One of them is Yadira “Pini” Villalvazo, who prosecutors identified as the leader of the Tijuana-based drug operation that imported and distributed heroin in North County, sending tens of thousands of dollars in proceeds back to Mexico.

Villalvazo, a Mexican citizen, attended Vista High School but was deported in 2002 after a federal drug trafficking conviction.

She was an associate of a Vista gang before becoming connected to the Sinaloa cartel, prosecutors said. She is also accused of supplying heroin — her specialty — to a distribution ring in Kingman, Ariz.

Many of the defendants are documented members of North County gangs in Oceanside, Vista, Fallbrook, Carlsbad, Encinitas, San Marcos and Escondido.

“We’ve seized heroin, methamphetamine and 25 firearms, including handguns, revolvers and assault rifles,” Robinson said. “These drugs and guns were being stored and sold in San Diego North County, including across the street from Vista High School.”

Authorities said the investigation also targeted methamphetamine traffickers, including organizations led by Sabrina Yzaguirre, Ivan Bazan and Jorge Enrique Jara Cervantes. Jara’s group is accused of shipping large quantities of the drug to Alabama and Tennessee for distribution.

“As we all know, we have an epidemic of heroin and methamphetamine abuse in our country, and that trend certainly is apparent here in San Diego County,” Robinson said.

She said the county’s heroin deaths have more than doubled in recent years, from 40 in 2005 to 90 in 2015.

Paramedics and some law enforcement officers in the county are trained to administer naloxone, a drug that counteracts the effects of heroin or other opioid overdoses. In 2015 alone, paramedics used naloxone 1,340 times, according to the U.S. Attorney’s Office.

Methamphetamine-related deaths in the county increased more than 80 percent between 2011 and 2015. In addition, about half of the adults taken into custody in the county in 2015 tested positive for meth at the time of arrest, Robinson said.