Three men described by police as gang members have been charged with first-degree murder in the death of a Gaithersburg woman who authorities said was kicked, choked, pummeled with heavy stones and thrown into the C&O Canal last week.

The body of Samantha Otoya Benavides, 19, who authorities said was an associate of the alleged killers, was found about 5 p.m. last Friday in the canal, floating near Violette's Lock in Montgomery County, U.S. Park Police said.

Gaithersburg police said Benavides had sometimes shared a residence in Gaithersburg with members of Mara Salvatrucha, or Salvadoran Gang, also known as MS-13.

Jose R. Rivas, 21; Carlos A. Aguilar, 22; and Raul G. Medina, 20, all of Gaithersburg, were arrested Tuesday and ordered held without bond in the Montgomery jail, police announced yesterday. Authorities said the men attacked Benavides on Dec. 5, kicking her in the face, choking her with a bandanna and striking her in the head with large rocks before dumping her in the water.

Police said Benavides was an associate of the gang but not a member. Detectives have not determined a motive for the killing, sources said, and they were unsure whether it was related to gang activity. Sgt. Scott Fear, a Park Police spokesman, said the investigation is continuing.

Gaithersburg police detective Patrick Word said Benavides' slaying was the first homicide attributed to members of MS-13 in Gaithersburg. He said the gang has been there since 1994 and boasts 100 to 150 members among five neighborhood factions.

"They usually like to commit property crimes," Word said. "They'll steal a car and sell it to a chop shop. They break into a car and sell anything valuable or keep it for their own personal use. Most of it is for financial gain."

Benavides, whose home was near the suspects' residence, had been periodically spending nights at the house with Aguilar and Medina, according to a police affidavit filed in Montgomery District Court.

On Dec. 5, the affidavit stated, Benavides got into a vehicle with Aguilar, Rivas, Medina and two other Gaithersburg men, identified as Eric Ramirez and Nino Dilbert. They were drinking Corona beer, police said, and were headed to Violette's Lock, where there is a popular towpath for hikers and bikers.

Investigators said in the affidavit that Ramirez and Dilbert, who have not been charged in the case, gave accounts of that day:

On the way to the canal, according to the affidavit, Medina told the other men that they should kill Benavides. Dilbert told police he thought Medina was joking, the affidavit said, but when they arrived at the lock and started walking along the towpath, Medina told Dilbert and Ramirez to go back to the car.

The two returned to the car, and while waiting for the others to return, they heard a bottle break and a woman scream, according to the affidavit.

Dilbert went back to the towpath, the affidavit said, and saw Aguilar and Rivas on top of Benavides, choking her with a white bandanna, while Medina kicked her in the head. Aguilar and Medina then picked up a large rocks and struck Benavides in the head, according to the affidavit.

Her body was found in the canal eight days later, authorities said. An autopsy showed she died from a combination of blunt force trauma to the head and water inhalation.

Mara Salvatrucha, which has thousands of members across the country, has often been accused of violence, but most of it has been directed at rival gang members who have encroached on Mara Salvatrucha's turf or criminal enterprises, said Jeffrey Riley, chief of the FBI's gang unit. The gang was formed in Los Angeles in the mid-1980s, made up mostly of Salvadoran immigrants who were fleeing the country's civil war, Riley said.

Local factions, such as the one in Gaithersburg, are loosely affiliated and have little allegiance to one another, authorities said. They have a large presence in the Washington area and have been linked to at least four killings in Northern Virginia.

Jose R. Rivas, 21, is charged with killing Samantha Otoya Benavides, 19, by beating and drowning her.Raul G. Medina, 20, is also charged. Police described the suspects as members of a Salvadoran gang.Also charged in the killing is Carlos A. Aguilar, 22. The suspects and the victim are all from Gaithersburg.