A shuttered Philadelphia prison that was built 120 years ago and once used inmates as test subjects for biochemical research is being readied in case space is needed to hold protesters arrested during the Democratic National Convention.

Tens of thousands of protesters are expected at the July 25-28 convention.

Officials with the city's prison system tell the Philadelphia Inquirer Holmesburg Prison can be used if needed for mass arrests. The prison was closed in 1995.

Inmates would be kept in the prison's recently renovated gymnasium. Cell blocks would not be used.

Officials say the gym has 100 beds, showers and air conditioning.

The city has decriminalized some minor offenses related to demonstrations, and officials aren't anticipating large numbers of arrests during the convention.