Authorities are investigating an allegation by the mother of "Modern Family" star Ariel Winter that her daughter's 18-year-old boyfriend had unlawful sex with the 14-year-old actress, according to sources familiar with the investigation.

The L.A. County Sheriff''s Department's Special Victims Unit also is separately examining whether Winter's mother, Chrisoula Workman, physically abused the teenage actress.

So far, detectives have not gathered any specific evidence to substantiate the allegations in either investigation involving Ariel, otherwise  known to millions as Alex Dunphy, the brainy member of "Modern Family's"  Dunphy family.

The investigations began last month after a judge awarded temporary guardianship of Ariel, whose real name is Ariel Workman, to her adult sister, Shanelle Gray, also an actress. Ariel, through her sister's attorney, alleged in a court filing that she was subject to ongoing physical and mental abuse by her mother. 

Three days after Ariel took legal action to split from her mother, Chrisoula Workman reported on Oct. 6 to the sheriff's Crescenta Valley station that her daughter's 18-year-old boyfriend had unlawful sex with the underage actress.

Chrisoula Workman contends she discovered her daughter in the guest bedroom of her Montrose home on Sept. 24 in bed with a young man, believed to be 18, according to sources not authorized to discuss the investigation.

The young man was described as the teenage actress' boyfriend of several months, according to the sources. According to sources, both the teenagers have denied doing anything unlawful.

Detectives also have been unable to substantiate Ariel's abuse allegations, but the investigation remains ongoing.

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-- Richard Winton and Andrew Blankstein, Los Angeles Times