(CNN) -- A three-day federal crackdown on child prostitution rings across the country has resulted in the recovery of 69 children and the arrest of 884 people, including 99 pimps, federal authorities said Monday.

Meanwhile, in Tennessee, authorities announced Monday they were arresting 29 individuals involved in gangs that trafficked underage Somali and African-America girls in a prostitution ring. The 29 people were connected to the Somali Outlaws, the Somali Mafia and the Lady Outlaws, officials said.

The three-day federal sweep, called Operation Cross Country V, involved 40 cities nationwide and is part of the Innocence Lost National Initiative, authorities said.

"Child prostitution continues to be a significant problem in our country, as evidenced by the number of children rescued through the continued efforts of our crimes against children task forces," said Shawn Henry, executive assistant director of the FBI's Criminal, Cyber, Response and Service Branch, in a written statement. "There is no work more important than protecting America's children and freeing them from the cycle of victimization. Through our strategic partnerships with state and local law enforcement agencies, we are able to make a difference."

The city where the most children were recovered was Seattle, Washington, with 16, said FBI Special Agent Jason Pack. Seven pimps were arrested there, he added.

Following Seattle were Tacoma, Washington, and Sacramento, California, each with seven child prostitutes retrieved by authorities, Pack said. Two pimps were arrested in Tacoma and three in Sacramento, he said.

The city with the largest number of pimps arrested was Detroit, with 10, Pack said.

To combat growing child prostitution, federal agencies formed the Innocence Lost National Initiative in June 2003 to address enterprises involved in the domestic sex trafficking of children. Those agencies were the FBI's Criminal Investigative Division, the Department of Justice's Child Exploitation-Obscenity Section and the National Center for Missing and Exploited Children.

There are now 39 Innocence Lost task forces and working groups throughout the country.

So far, those units have recovered 1,250 children, and the initiative has resulted in 438 indictments, 625 convictions, 153 criminal enterprises disrupted and 58 successfully dismantled, authorities said. Convictions have resulted in sentences ranging up to 25-years-to-life and in the seizure of more than $3 million in assets, authorities said.

The most recent sweep, over a 72-hour period ending Sunday night, was the fifth such law enforcement operation, said Pack.

"Once again, Operation Cross Country has awakened the nation to the fact that today American children are being marketed and sold for sex in American cities," said Ernie Allen, president of the National Center for Missing and Exploited Children, in a written statement. "These kids are victims. This is 21st century slavery. We are proud to be a part of this extraordinary partnership to rescue children, save lives and bring the pimps and operators to justice."

The FBI says that at least 25 percent of adult prostitutes were enticed into the illegal activity as juveniles.

In Tennessee, federal authorities said the gangs transported the minor girls from Minneapolis, Minnesota, which has a large Somali immigrant community, to Nashville, Tennessee, for prostitution over a 10-year period. Some of the girls were 13 years old or younger.

"I would call this one of the more significant cases that we investigated," said John Morton, director of the Immigration and Customs Enforcement agency.