A Roanoke woman accused of supplying the heroin on which a 17-year-old and 19-year-old overdosed pleaded guilty Thursday in the latest stage of a federal crackdown on distribution of the drug in and around the city.

Cynthia Kaye Nichols, 41, was the fifth of 11 defendants in three linked heroin cases to plead guilty in U.S. District Court in Roanoke. Authorities said the cases spotlight an alarming growth in the use of heroin by young people, such as the teens whose overdoses -- and eventual recovery -- were detailed in testimony Thursday.

The first of two overdose episodes tied to Nichols occurred on July 1, Assistant U.S. Attorney Don Wolthuis said. Roanoke County dispatchers received an emergency call to an apartment in Southwest Roanoke County, where a 19-year-old girl was found lying on the floor, unresponsive and with her lips turning blue. She was revived, Wolthuis said.

Investigators determined that the teen was a heroin user whose usual practice was to split a bag of the drug with her boyfriend. Using heroin bought from Nichols, she this time split a bag with a 17-year-old who injected the drug into her, then later injected the contents of a second bag. With approximately three times her usual dose, she passed out and woke up in the hospital, Wolthuis said.

The second incident occurred on Oct. 23 when the 17-year-old involved in the first episode bought three bags of heroin from Nichols in the parking lot of a Wendy's restaurant on Hershberger Road. The teen injected the heroin inside a car in the parking lot, then passed out as his girlfriend drove along Interstate 581, Wolthuis said.

She raced to the Awful Arthur's at Towers Shopping Center, slapping her boyfriend as he turned blue in the passenger seat, Wolthuis said. A police officer happened to be near the restaurant, and when the girlfriend summoned him, he was able to keep the 17-year-old alive and get him to a hospital.

Both victims recovered from the overdoses, Wolthuis said. Neither of the teenagers was charged with any crimes by federal or state authorities, he said.

Nichols' guilty plea to a charge of conspiring to distribute heroin that led to a serious injury will bring a mandatory minimum sentence of 20 years in prison and a fine of up to $1 million. A second count of the same charge and several distribution charges will be dropped under Nichols' plea agreement.

The only way to reduce the sentence below the mandatory minimum, Wolthuis said after the hearing, is to render substantial assistance to the government's prosecution of other cases.

Nichols' sentencing is set for July 13.