A 20-year-old man was being held on $100,000 bond after allegedly posing as a middle school girl and trying to extort sex from children in the Seattle area.

Pedro Pablo Navarro, a homeless man from Burien, Wash., was arrested March 7, Seattlepi.com reported.

A Seattle detective said in a court document Navarro had contacted a 13-year-old middle school student on Facebook Feb. 6, sent a friend request and the next day told the boy of his fictitious sister, who he called "Samantha," and said she wanted to text with him.

Navarro, posing as "Samantha," tried to pressure the boy into sending him nude photos while offering to have sex, but when the boy refused, Navarro threatened to have the boy arrested by the fictional FBI agent father of "Samantha," the detective said. The boy asked if he could do anything to make "Samantha" leave him alone and was told he would have to let her brother molest him on video, the detective said.

Navarro, the detective said, demanded the phone numbers of six of the boy's friends and the boy gave him numbers of at least four children ages 12-14. At least three of the children received text messages the next day from Navarro posing as "Samantha," the detective said.

Charging documents say Navarro, posing as "Samantha," had demanded sexually explicit photos or solicited sex from four of the boy's friends.

The Seattle detective said Navarro is believed to have contacted as many as 10 additional children and the investigation is continuing.

Authorities said Navarro also is accused of threatening harm to a 14-year-old Burien boy unless he sent sexually explicit photos. The boy told detectives he had received a message from someone claiming to be a 12-year-old girl.

The boy was afraid his house could be burned down and sent a photo of himself, charging documents said.

Navarro has been charged with five counts of communication with a minor for immoral purposes and two counts of extortion.

He was convicted three years ago of molesting a 13-year-old boy in Idaho, Seattlepi.com said.