A man convicted of sex crimes in Canada may now be a suspect in a sexual assault case involving a 16-year-old boy in the States.

Michael Stanley was arrested early Tuesday morning in Washington after police responded to reports of a man yelling in a residential neighbourhood in West Seattle.

When police arrived, they contacted the man in the alley and say he was very intoxicated.

"He was belligerent and combative towards our officers and in talking to some of the witnesses he had actually threatened to do them bodily harm so based on that he was arrested for the misdemeanor charge of harassment and at that point, after he was arrested, we then determined that it was indeed Michael Stanley," said Detective Mark Jamieson, Seattle Police Department.

Jamieson says once Stanley was already in custody and in the King County Jail in Seattle, they were contacted by a 16-year-old male who told them he had been in contact with Stanley before the 911 calls.

"He had met up with Mr. Stanley at a nearby grocery store and then had walked with Mr. Stanley, eventually ending up in that very alley. Mr. Stanley allegedly plied the young man with alcohol and then at some point attempted to assault him, including a sexual assault," said Jamieson.

Police say the young man was able to fight Stanley off to get away and later learned of the arrest in the alley and contacted police.

"He was booked into jail for harassment, but based on the new information our detectives are working to amend those charges and most likely he's going to be charged with some sort of sexual assault which is a felony," said Jamieson.

Stanley was wanted on a Canada-wide warrant for breaching the conditions of his release in Edmonton and crossed over the border into the United States through B.C. earlier this month.

On Monday, Washington State’s sex offender register listed him as a transient “level 2” offender.

Authorities are now working to determine how this latest incident will affect his offender status.

(with files from Bill Macfarlane)