A person has died and three others are in hospital after an explosion triggered a fire that engulfed an apartment block in Sydney’s inner-west.

Fire and Rescue NSW said it received calls about an explosion and fire in a block of units in Young Street at Croydon around 5.45am on Monday.

Twelve fire trucks and more than 40 firefighters arrived to find the fire had engulfed a ground floor apartment and was spreading to units above.

Trapped residents living on the third floor were rescued by firefighters on ladders and about 30 people were evacuated.

A resident says she was getting ready for work when she head the explosion.

“All of a sudden I felt the house shake and very loud noises and glass shattering,” she told ABC TV.

“I thought the back of my house was collapsing so just ran out with my family and then went down the back to see what was going on.”

She saw a four metre “big ball of fire” before yelling for people to evacuate.

A resident, a firefighter and a police officer were taken to hospital and are reported to be in a stable condition.

Fire crews extinguished the blaze and found body inside the ground floor unit where they suspect the fire started.

Fire investigators are working with NSW Police to determine the cause of the incident.

– AAP