Image copyright Reuters Image caption Richard Bratz of Delaware state police issued a statement about the hostage standoff at James T Vaughn Correctional Center in Smyrna

A prison officer who died during a US hostage standoff warned his colleagues that inmates had set a trap, union officials have said.

Sgt Steven Floyd, 47, had been placed in a closet by inmates, but he shouted to fellow officers and told them to get out of the building, officials said.

Geoff Klopp, of the Correction Officers Association of Delaware, added that Sgt Floyd's actions had "saved lives".

Earlier, officers stormed the prison block, ending a 24-hour standoff.

Image copyright Facebook Image caption A Delaware corrections officer shared this photo of Steven Floyd on Facebook with the comment: 'His professionalism was beyond reproach and was one hell of a guy who was fun to talk to'

Prisoners in C Block at the James T Vaughn Correctional Center in the town of Smyrna took four staff and fellow inmates hostage on Wednesday.

One of the prisoners told a local newspaper they were protesting against US President Donald Trump.

On Thursday morning, a female prison employee was rescued and taken to hospital as police raided C Block.

Sgt Floyd, a 16-year veteran of the Department of Corrections, was found unresponsive after tactical teams used construction equipment to breach a wall and enter the building.

"Sgt Floyd Sr was a father, a grandfather, a loving husband. He worked overtime three to four times a week to put his kids through college, through masters school - anything his kids or his wife wanted, or his grandkids. He loved them with all his heart," said Mr Klopp.

Authorities have not said how he died.

"My prayers all day yesterday was that this event would end with a different result. But it didn't," Governor John Carney said on Thursday morning.

Image copyright Reuters Image caption Emergency vehicles surrounded the prison

The governor called the situation "torturous" and promised a full investigation.

The rescued employee was found less than two minutes after the raid began.

She has been identified only as a female counsellor with the Delaware Department of Corrections.

Some inmates "actually shielded this victim and ensured her safety", said Robert Coupe, secretary of the Delaware Department of Safety and Homeland Security.

Officials say that she is in hospital, and is "alert and talking" after being rescued at around 05:00 local time.

At one point during negotiations authorities turned on the water, so that inmates could bathe and drink, however the inmates used the water to fill metal footlockers, which were then used to barricade prison hallways, officials said on Thursday.

Image copyright AP Image caption The prison remained on lockdown following the raid, as investigator search every prison cell in C Block

Officials have not yet determined the attackers' motivation, but have said the weapons used were "sharp instruments".

Two of the prison employees and 46 inmates were released on Wednesday and overnight by the hostage-takers at the facility, which is the largest prison for men in the north-eastern state.

Three maintenance workers hid in the basement and were not discovered by the hostage takers.

They were able to get to the roof late on Wednesday, and were rescued by tactical teams.

Earlier in the day, inmates called the News Journal newspaper in Wilmington to explain their actions and make demands.

In that call, an inmate said their reasons "for doing what we're doing" included "Donald Trump. Everything that he did.

"All the things that he's doing now. We know that the institution is going to change for the worse."

He also demanded education, a better rehabilitation programme and called for inmates to be granted scrutiny of the prison budget.

Authorities said they were not sure if all the inmates had been held against their will.

All 120 inmates housed in the block should be considered "suspects", he said.

It was not the first hostage situation at the prison.

In 2004, a 45-year-old inmate at the prison raped a counsellor and took her hostage for nearly seven hours, before he was shot dead by a sharpshooter.