Clinton — A Clinton man was arrested this morning on charges that he sexually assaulted a child at his home.

William Motta Sr., 67, of 159 Glenwood Road, was charged with first-degree sexual assault, second-degree unlawful restraint and risk of injury to a minor.

Police said that Motta had a previous conviction in the 1970s and 1980s for the same type of activity. He was not on the sex offender registry because the previous assaults were prior to the sex offender registry statute.

Police said Motta was arrested after a four-month investigation into the sexual assault allegations. The child was an acquaintance of Motta and the assault occurred at Motta's residence.

The parents of the child were not aware of Motta's previous convictions, police said.

Motta was held in lieu of $500,000 and arraigned before Middlesex Superior Court Judge David P. Gold. The judge kept the bond at $500,000, continued the case to March 17 and issued a protective order prohibiting Motta from having contact with the alleged victim.