Inmates were holding two people hostage at a Delaware prison on Wednesday night in a standoff that began in the morning and left at least one prison employee injured, officials said.

The hostages were taken at the James T. Vaughn Correctional Center, near the town of Smyrna, between Wilmington and Dover. It is the state’s largest prison, with 2,500 inmates in minimum-, medium- and maximum-security units.

At a news conference on Wednesday night, officials revealed that a total of 27 inmates had been released by the hostage-takers, but it was unclear whether they had been held against their will and how many inmates remained.

Officials said four staff members had initially been taken hostage. Early accounts put that number at five, though officials said one person had not been accounted for at first but was later found to be safe.