Federal agents on Wednesday arrested the suspected leaders of a Des Moines street gang after a months-long investigation into violent crime and drug dealing.

In total, 15 men were charged after the FBI executed warrants around Des Moines. The suspects were in federal custody, mostly on charges of conspiring to distribute cocaine.

Those arrested include twin brothers Daeron and Marshaun Merrett, whom the FBI called the leaders of C-Block, a neighborhood gang with territory encompassing the Cheatom Park area in Des Moines. The group is affiliated with the Crips.

Rachel Scherle, an assistant United States attorney, said the investigation will be discussed at a news conference Thursday with the FBI and U.S. Attorney Marc Krickbaum. The office called it a "significant" investigation.

Scherle told the Des Moines Register she did not know how many people had been arrested but called one dozen a close estimate.

Members of the gang are responsible for killings, shootings, robberies and other crimes, according to court records. A 75-page FBI affidavit outlines how members allegedly obtained cocaine from Chicago and Gary, Indiana, on a frequent basis to distribute throughout Des Moines.

Since May 2016, investigators have intercepted phone calls and text messages and used surveillance and informants to penetrate the group, records show.

The affidavit cites purchases of powder cocaine made at one of the men’s homes and another in the parking lot of a West Des Moines business. It also mentions a December traffic stop, during which Des Moines police officers found two handguns in a vehicle carrying some of the men.

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An expert with the Bureau of Alcohol, Tobacco, Firearms and Explosives confirmed the guns were made outside of Iowa and therefore crossed a state line, records show.

In intercepted calls, some of the men discussed drug deliveries. In one, Freddie Frencher told Daeron Merrett that someone complained about the quality of their cocaine, calling it baking soda, according to court documents.

"It’s not baking soda," Merrett said before he suggested Frencher taste it, according to the affidavit. "You know I ain't come like that."

"My s--- numbing up right now, my tongue," Frencher said, mentioning the reaction an agent described as a typical effect of cocaine when licked, according to the records.

"Alright, so what are they talking about?" Merrett asked.

When one had suggested they get their drugs from out of state, Hunt told Daeron Merrett the people he was talking to would let him examine the high-quality cocaine before he pays for it, cutting open the vacuum-sealed package — a common way to bundle the drug — and weighing it, a task force officer wrote.

Two of the men took at least four trips to retrieve cocaine from the Chicagoland area, investigators said. On one drive back, Daeron Merrett and Marcus Hunt were stopped by officers; Merrett told his broker his "heart was in his stomach" because of the drugs in their vehicle, according to the affidavit.

In one intercepted call, one man told the other he would make a drug trip in the morning because they "didn’t do s--- at night," considering new customers could rob them, the task force officer wrote in court records. One man also complained that another "be talkin’ too much on the phone" about their dealings, according to the records.

Investigators obtained messages that agents believe show the men negotiating deals, such as trying to get nine ounces of cocaine for $8,500 or 10 ounces for $10,000.

Authorities also believe some of the men planned to rob a residence for marijuana, texting with the term "lick," which is slang for robbery or burglary.

Those arrested in the investigation include:

Daeron Johnson Merrett, 31

Marshaun Jordan Merrett, 31

Barry Adair, Jr., 29

Freddie Lee Frencher Jr., 28

Johnathan Frencher, 26

Marcus Antwon Hunt, 37

Jose Antonio Sanchez Jr., 26

Conrad Fred Taylor Jr., 32

Jhamel Donta Booker, 35

Cornelius Neal Pope, 40

Peter E. Cooper Jr., 32

Walter Stefon Burgs, 48

Antowan Leon Taylor, 40

Paul Joseph Castelline, 33

Cordney Smith, 43

All except Marshaun Merrett are accused of controlled-substance crimes.

Freddie Frencher was also charged with interference with commerce by threats or violence. Marshaun Merrett was accused of illegally possessing ammunition as a felon.

Many of the defendants are associated with numerous other prosecutions, by federal and state authorities, in online court records.

The FBI affidavit accuses at least three other people of crimes; there was no indication that they were in custody Wednesday. Authorities declined to comment about what locations were searched Wednesday and the success of those efforts.

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Des Moines police have attributed violent stretches in the city in part to gang activity for decades. In 2017, when Des Moines recorded more homicides than it had in a single year since 1978, police said shootings had spiked because of conflicts between loose-knit street gangs. C-Block and Heavy Hittas are two of the better-known gangs.

Sgt. Paul Parizek, a Des Moines police spokesman, said he could not comment on the investigation before the news conference Thursday. Other agencies involved included Altoona police and the sheriff’s offices in Polk, Story and Dallas counties.

Ako Abdul-Samad, a state legislator who has spent years combating gang issues while running Creative Visions, a Des Moines social services agency, said the arrests show Iowa is not immune to the drug trade.

He assumed the gang was organized, considering the extent of the investigation.

"That organization, like any corporation, has a contingency plan in place," Abdul-Samad said. "The question is what is the contingency plan — who's going to take the place? The arrests won't stop drug activity, but it slows it down."

This story includes information from the Associated Press.