A Biddeford man accused of prostituting a woman in her late 50s and keeping a written contract threatening to violate her with a “claw hammer” if she worked for anyone else was arrested Monday on a federal interstate pimping charge.

Leo Grondin, 48, was brought to U.S. District Court in Portland on Monday afternoon to face a felony charge of transporting an individual in interstate commerce with intent that she engage in prostitution.

Magistrate Judge John H. Rich III ordered that Grondin remain in the custody of the U.S. Marshals Service pending a detention hearing on Friday.

A Biddeford police officer assigned to a federal Homeland Security task force to investigate human trafficking first began tracking Grondin after discovering his phone number in numerous online advertisements for commercial sex and escort services, according to court documents unsealed Monday after Grondin’s arrest.

Police got a break in the investigation on July 9 when the daughter of the woman called the Biddeford Police Department to share what she had discovered about her mother, Biddeford police Officer Ronald Phillips wrote in an affidavit seeking a warrant for Grondin’s arrest.

“(The daughter) reported that her mother had recently requested her assistance in installing an application on her cellphone. In the process of installing the application on (her mother’s) phone, (the daughter) discovered email conversations regarding prostitution, websites for escort services and ads promising ‘in-home specials for prostitution’ that included (her mother’s) and Grondin’s home address. Based on the emails, (the daughter) believed that (her mother) was both helping Grondin run a prostitution ring and engaging in prostitution herself,” Phillips wrote in the affidavit. “After she confronted (her mother) about the emails and their content, (her mother) admitted to her that Leo Grondin was prostituting her and other women, and that Grondin was mean to her if she did not engage in prostitution.”

The daughter also shared with police a handwritten contract she had discovered at her mother’s house, between Grondin and her mother. In the contract, her mother promised not to engage in prostitution without Grondin and Grondin promised not to pimp without her mother. Other documents the daughter shared included handwritten drafts of prostitution advertisements with Grondin’s phone number, Phillips wrote.

Police tracked Grondin and the mother to a hotel in Dover, New Hampshire, on July 17 after discovering another online advertisement with Grondin’s phone number and a picture of the mother. Police took Grondin into custody there on an outstanding arrest warrant issued by New Hampshire authorities. The woman agreed to let police give her a ride back to Maine and tell them about the prostitution business, the affidavit states.

Grondin faces 10 years in federal prison and a fine of as much as $250,000.