MTA Police have made an arrest in the robbery and sexual assault of a teen at a Long Island Rail Road station nearly two years ago.

The suspect, 23-year-old Ariel Perez of Wyandanch, was taken into custody last month, according to Suffolk District Attorney spokesman Robert Clifford.

Perez is charged with locking an unidentified 16-year-old boy in the bathroom of the LIRR's Northport station in August 2011.

According to Clifford, Perez stole $110 from the victim and then sexually abused the teen.

Perez has pleaded not guilty to robbery and sex abuse charges. If convicted, he could serve up to 25 years in prison.

It wasn't immediately clear if he had an attorney.

A tip led investigators to Perez, according to a source close to the case. Perez was arrested in Islip on Jan. 16.