Two U.S. senators are calling for the release of a political activist, with ties to Philadelphia, from a Detention in Juba, South Sudan.

Sen. Cory Booker, D-N.J., and Sen. Chris Coons, D-Del., put out a joint statement on Wednesday saying that they want the South Sudanese government to free Peter Biar Ajak.

Ajak is a peace activist, one of the “Lost Boys of Sudan” who graduated from Central High School and La Salle University in Philadelphia.

Ajak’s family put out a statement saying he was arrested while trying to board a plane in Juba to Awiel earlier this week. It’s believed he was arrested for criticizing the South Sudanese government.