Terrified guests were forced to walk down flooded stairwells in the dark when water gushed from 18 floors of their Melbourne CBD hotel last night

Emergency services were called to the 33-storey building on City Road in Southbank around 10pm after reports of significant flooding.

Fire crews arrived to find a heavy stream of water cascading from the front of the building, prompting emergency works to evacuate the 120 people inside.

Terrified guests were forced to walk down flooded stairwells in the Melbourne CBD hotel building last night. Picture: 9NEWS (Nine)

A Traralgon man is accused of opening up the hydrants on 18 floors. Picutre: 9NEWS (Nine)

A 27-year-old man is accused of turning on every fire hydrant from the ground floor of the building to the 18th floor, causing thousands of litres of water to flow into the building’s hallways.

He then barricaded himself in an office before police were called and he was arrested.

After the guests were evacuated, firefighters worked at turning the hydrants off and limiting water damage to the premises.

One maintenance worker was also taken to hospital during the clean-up this morning after being hit in the face by a jet of water from a burst pipe while working on the repairs.

Guests have been left on the street with nothing but wet clothes. Picture: 9NEWS (Nine)

The building remains unoccupied and without water as the clean-up efforts continue. Picture: 9NEWS. (Nine)

It is believed the building remains without running water and will stay unoccupied until a building surveyor attends the scene to assess the damage.

Families with young children and babies were among the people evacuated from the building. They have been placed in nearby hotels but are left without baby formula and fresh clothes.

Those with flights out of Melbourne today have been escorted up the dark and narrow stairwell to retrieve their possessions. Hotel management is working to get approval to allow everyone back in.

Emergency services were called to a Melbourne CBD apartment block overnight following reports of significant flooding. Picture: 9NEWS. (9NEWS)

A 27-year-old man had allegedly turned on every fire hydrant in the building from the first floor to the 18th floor. Picture: 9NEWS. (9NEWS)

The only damage is to the carpets outside the stairwells. The rooms remain undamaged.

One guest told 9NEWS: "It was pretty scary, we had to duck under a broken door to get out.

Another woman said: "We got to the 18th floor and started getting rained on, and the water got deeper as we went down further"

120 people were evacuated from the premises as thousands of litres of water flowed through the building and out of the front door. Picture: 9NEWS. (9NEWS)

The man allegedly responsible for the flooding barricaded himself in an office before he was arrested. Picture: 9NEWS. (9NEWS)

"Everyone was just so patient and it was so nice to see everyone pulling together".