(Reuters) - Police stormed a prison building in Delaware on Thursday to end a hostage standoff by prisoners that left one corrections officer dead and another being protected by inmates.

The officers were found in separate rescue operations by 5:30 a.m. on Thursday from the James T. Vaughn Correctional Center in the town of Smyrna, Delaware Department of Correction Commissioner Perry Phelps told a news conference.

They had been among four officers taken hostage in the inmate uprising that broke out about 10:30 a.m. on Wednesday in the prison’s C building. Two of the officers were freed on Wednesday after negotiations.

Delaware Governor John Carney said in a statement that the situation had been “long and agonizing.”

“Our priority now will be to determine what happened and how this happened ... and we will make whatever changes are necessary to ensure nothing like it ever happens again,” Carney said.

Sergeant Steven Floyd, a 16-year veteran of the correction department, was found unresponsive after state police retook C building, Phelps said. Floyd, 47, was later pronounced dead but it was not immediately clear how he died.

A female officer was rescued uninjured after authorities breached the building, said Department of Safety and Homeland Security Secretary Robert Coop.

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“There were inmates that actually shielded this victim,” Coop said.

Police retook the building after knocking down makeshift walls of metal lockers filled with water that inmates erected at the building’s entrances, Coop said.

The incident, which prompted a lockdown of prisons statewide, started at about 10:30 a.m. on Wednesday when a corrections officer radioed for help from the C building, which houses 120 inmates.

Hostage negotiators assisted by agents from the Federal Bureau of Investigation persuaded the prisoners to free two corrections officers on Wednesday, Coop said. One of those officers was hospitalized with non-life threatening injuries.

Three maintenance workers sneaked to the roof of the building after hiding in a basement and were rescued, he said.

It is too early to determine a motive for the uprising, Coop added, but he confirmed media reports that inmates were demanding better living conditions.

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The prison, 40 miles (64 km) south of the city of Wilmington, holds about 2,500 inmates, including some with death sentences.

The one-story C building, with three long halls and a central communal area, provides intermediary housing to maximum-security inmates moving to lower security facilities, Coop said.

All inmates were removed from the building, where investigators were sweeping cells for evidence, Coop said. The inmates are being treated as suspects, he said.

The Delaware Department of Correction said in a statement it “continues to operate under emergency procedures.”

(This version of the story has been refiled to add Delaware to headline)