Prevatt was charged with two counts of threatening arson by use of an explosive device, and Reynolds was charged with two counts of conspiracy to commit a threat of arson by use of an explosive device.
Both were charged with two counts of possession of controlled dangerous substances. Police identified the substances as suspected marijuana and MDMA, which is known as Ecstasy.
They also were charged with one count of felony theft by possession of stolen property.
Prevatt was being held Saturday in the Washington County Detention Center on $1 million bond. The bond is for the current charges and for a 2000 arrest warrant from Hagerstown, according to a Washington County District Court commissioner.
Reynolds -- who is in the late stages of pregnancy, police said -- was at the detention center on $250,000 bond.
They are scheduled to appear in court for bond reviews on Monday at 1 p.m.
Prevatt claimed he was armed during the standoff and made bomb threats, but police said they didn't find any weapons or explosives in the room.
However, police reported finding drugs and stolen property, including jewelry, cameras, electronic equipment and coins, in the room.
Some items have been matched to an Aug. 11 burglary from a home west of Hancock, when about $17,000 worth of property was taken, according to a police press release.
Prevatt claimed during some threats that he would harm a second woman in the room, but she didn't exist, police said.
Authorities have said Prevatt is wanted on burglary and larceny charges in South Carolina, Massachusetts, Virginia and Maryland. Massachusetts officials plan to file a detainer next week to keep Prevatt in custody, police said.
Another warrant, from July 2000, is for first-degree burglary connected to electronics equipment taken from Guilford Avenue in Hagerstown. Prevatt was living in Hagerstown at the time.
The Associated Press reported that Prevatt served a month in jail in Worcester County, Mass., in March and was released after pleading guilty to a misdemeanor charge of larceny under $250.
An arrest warrant was issued for him in May after his DNA matched DNA at a Massachusetts home burglarized in January, according to the AP.
Joseph Michael, Washington County's deputy state's attorney, said Friday night that authorities were trying to verify that Reynolds is the same person wanted on a South Carolina warrant for petty theft.
The standoff in Hancock began Wednesday night when a state trooper at the Hagerstown barrack heard that Prevatt and his pregnant girlfriend might be at the motel.
When two state troopers and two Washington County Sheriff's Department deputies knocked on the door to Prevatt's room, the lights went out and a man inside threatened to kill officers who tried to arrest him on warrants, police have said.
In the ensuing hours and days, dozens of police officers from Hagerstown, Washington County and other parts of Maryland were called in to help, along with the FBI.
A Baltimore County Police Department tactical team caught Prevatt Friday night when he opened his door to get food. Officers shot him with a Taser electronic device and forced their way through the front door, while other officers set off an explosive device to get in the back door, police said.
Guests in 12 rooms at the motel were evacuated and later moved to the nearby Super 8 motel to stay. The American Red Cross and the Hancock Interfaith Service Coalition paid for meals and new motel rooms.
Guests were allowed back to Americas Best Value Inn Friday night to retrieve their belongings and vehicles.
The U.S. 522 bridge, which was shut down during the standoff, also reopened Friday night.
TV news gear used to try to end standoff
Police used TV news equipment to try to get James A. Prevatt III to come out of his room at Americas Best Value Inn in Hancock early in the hostage standoff that ended after 45 hours.
At one point during negotiations with police, Prevatt said he would come out if his exit would be on the TV news, Maryland State Police spokesman Greg Shipley said Saturday.