Picture used for illustrative purpose only.

A man was trapped inside a steel-reinforced concrete jewellery vault in New York City overnight after firefighters had to abandon an attempt to rescue him for safety reasons.

Fortunately, the vault was on a timer and opened on its own Wednesday morning, officials said.

The fire department was called to the midtown Manhattan building on Tuesday evening after the man became trapped while trying to access his safe deposit box, Assistant Fire Chief John Sarrocco said.

The building at 580 Fifth Avenue is known as the World Diamond Tower and houses several jewellery businesses. Sarrocco did not explain how the man became trapped.

Fire and police department personnel were in communication with the man inside the vault and could watch him on a security camera.

Sarrocco said the fire department's rescue units have tools that would be able to break through the vault's 76-centimetre steel-reinforced concrete walls.

"The process was started to breach the wall at the vault,” he said in a news conference at the scene.

After about 10 hours, Sarrocco said, the firefighters reached the steel plating and decided to hold off going any further, fearing their rescue attempts could harm the man trapped inside.

"The problem with the plating is we’d have to use our torches," he said, "which would affect the environment for that person inside the vault.”

The doors opened as scheduled around 7:00 am and the man was freed unharmed, Sarrocco said.

Associated Press