Maryland State Police are investigating the 12th prisoner death this year and third this month, officials said Monday.

Jordan Polston, 32, was found unresponsive in his cell at North Branch Correctional Institution in Cumberland on Sunday morning, state police said in a news release. Another person incarcerated at the Western Maryland facility is a suspect in his death, officials said.

Wenhui Sun, a 36-year-old Californian serving time in Maryland for his involvement in a gold bar scam, died Dec. 16 amid an altercation at the Maryland Correctional Training Center in Hagerstown. And 23-year-old Deon Smith died Dec. 13 while incarcerated at Jessup Correctional Institution in Anne Arundel County.

Polston is the fourth prisoner to die this year at North Branch Correctional Institution. Patrick Candeloro, 38, Billy Sorrow, 50, and Elias Alvarado, 30, also died at the Cumberland facility.

That’s the most of any prison in the state. Eastern Correctional Institution and Jessup Correctional Institution have three each. In addition to Smith’s, state police are investigating the deaths of 61-year-old Warren Michael Griffin and 42-year-old Brian Bell at Jessup Correctional Institution.

At Eastern, state police are investigating the deaths of prisoners Ray Stephen Oselmo, 36, and Donyell Morris, 24. Shane Lanham, 28, also died there this year, and another prisoner at the Somerset County facility was charged for his death.

Lawrence Antonio Borom, 21, died while imprisoned at Roxbury Correctional Institution earlier this year, the only known case under investigation by state police at the Washington County center.