Two more men were arrested Monday on arson (search) charges as the number of suspects accused of setting dozens of fires at an upscale suburban Washington housing development continued to grow.

Authorities also said they had interviewed or planned to question around 10 additional people who may be connected to the fires two weeks ago in Indian Head (search) that caused an estimated $10 million damage.

Roy T. McCann, 22, of Waldorf, and Michael E. Gilbert, 21, of Fort Washington, were arrested Monday, according to the U.S. Attorney's office in Baltimore. McCann and Gilbert will appear on federal charges before a magistrate judge in U.S. District Court in Greenbelt on Tuesday.

Three suspects arrested over the weekend made initial appearances Monday. Magistrate Charles B. Day ordered Michael M. Everhart, 20, of Waldorf; Jeremy D. Parady, 20, of Accokeek; and Patrick S. Walsh, 20, of Fort Washington, held until a detention hearing Thursday.

Parady's lawyer, Tim Sullivan, said he would argue that his client should be released on bond. "He's a volunteer firefighter who has taken an oath to protect lives and protect property and he's innocent of these charges," Sullivan said.

A fourth suspect, Aaron L. Speed, 21, was arrested last week. He has a detention hearing scheduled Tuesday. Speed worked as a security guard at the Hunters Brooke site, while Parady was a firefighter with a volunteer fire company in nearby Accokeek.

Two possible motives, race and revenge, are among the theories that have emerged during questioning of the four men in custody, an official has said.

The Dec. 6 fires at an upscale housing development under construction destroyed at least 10 houses and damaged 16 others, Maryland's largest case of residential arson. No one was injured.

According to affidavits, Parady, Walsh and Everhart, all arrested Saturday on arson charges, initially denied their involvement in separate interrogations but changed their stories after they were confronted with evidence.

All three told investigators that additional "acquaintances" were involved.

Parady allegedly told investigators his job was to be "the wheels" of the operation, according to the affidavit.

Dogs had found evidence of accelerants in two cars that belong to Walsh, the documents state. Walsh allegedly said "then I guess you got me" when investigators asked him what would happen if accelerant-sniffing dogs "hit" on the cars.

Everhart said he knew in advance of the plot and was at the scene but left before any homes were torched, according to the affidavits.

The documents said the four men and others met outside a nearby restaurant and drove to the development in two cars, at least one of which was owned by Walsh. Among other things, the affidavits said, they had matches, road flares, butane torches and gas cans.

They kicked in the doors of the houses, poured a pool of accelerant inside and ignited a trail from the pools to the doors, authorities said. Lab tests detected traces of two flammable liquids — toluene and methyl isobutyl ketone, both solvents with a number of industrial uses — on debris.

A federal law enforcement official, speaking on the condition of anonymity, said Sunday that two of the men allegedly made racial statements. The suspects are white, and many of the families moving into the homes are black.

However, Michael Campbell, a spokesman for the Bureau of Alcohol, Tobacco, Firearms and Explosives, said several other factors also were under consideration.

The official who spoke on condition of anonymity said Parady tried unsuccessfully to get a job with Lennar Corp., the company building the houses. Speed allegedly told investigators he was angry with his employer, Security Services of America, because it did not show enough sympathy after his infant son died this year.

Initially, there was speculation the fires were set by environmental extremists because some critics had complained the houses threatened a nearby bog. But no evidence has been found to support that theory, police said.