Mundo Deportivo in Spain reports that only a formal announcement is left in the deal between the two clubs.
Joselu had a year left on his deal at the St. James' Park club.
However, he was not seen as a regular first team player under Rafa Benitez.
The 29-year-old will command a fee of roughly £1.8 million.
While it is unclear when an announcement will be made, the Spanish source indicates that only a few legal deadlines are left before the move is finalised.