A large fire has swept through a bag factory in the Indian capital Delhi, killing 43 workers, officials say.

The blaze broke out at the four-storey building in the city’s congested old quarter early on Sunday morning.

At least 100 people were sleeping inside the factory, which mainly makes school bags, when the fire started. More than 60 have been rescued.

Prime Minister Narendra Modi called the fire “horrific” and sent his condolences.

Delhi’s firefighters received the first call about the fire at 05:22 local time on Sunday (23:52 GMT Saturday).

The fire began on the lower storeys, spreading rapidly to the third floor where workers were sleeping.

The area where the factory is located – Azad Market – has many narrow alleyways, which made it difficult to reach the blaze.

Rescuers had to carry out victims on their shoulders one-by-one, BBC Hindi’s Dilnawaz Pasha reports from the scene.

It is not clear what caused the blaze but an investigation has been ordered. One witness blamed a short circuit.

Scores of injured people are now being treated in the city’s hospitals.

Victims’ relatives have been scrambling for information. One man told India’s PTI agency his brother was inside.

“I got a call from his friend informing that he has been injured in the incident. I have no clue which hospital he has been taken to,” he said.

Indian cities have often seen deadly fires, with poor planning and lax enforcement of safety regulations major factors.

Indian politicians have been expressing their horror at the blaze.

“The fire in Delhi’s Anaj Mandi on Rani Jhansi Road is extremely horrific,” Prime Minister Modi tweeted.

“My thoughts are with those who lost their loved ones. Wishing the injured a quick recovery. Authorities are providing all possible assistance at the site of the tragedy.”

Home Minister Amit Shah called it a “tragic loss of precious lives”.