Rescuers are digging through the rubble a day after a residential building collapsed in the Indian capital, Delhi, killing at least seven people.

It's not clear how many people were inside the five-storey building in south-west Delhi - or if there are still people under the debris.

Eyewitnesses told local media on Sunday that two-to-four dozen people were inside, but no official numbers have been shared. Authorities have confirmed 12 people were taken to hospital and that seven died while others are receiving treatment.

Delhi Chief Minister Rekha Gupta said "accumulation of water, combined with ongoing repair work in the basement" of the building, Hostel Daze, caused the collapse.

The building owner has been arrested and five senior civic officials of Delhi Municipal Corporation (MCD) have been suspended following the tragedy, Gupta added.

The building in the Satya Niketan neighbourhood of south-west Delhi, which sits a short distance from Delhi University's south campus which has five colleges, came down around 13:30 local time (08:00 GMT) on Sunday.

A majority of the residents were students and many were thought to be in their rooms at the time of the collapse as there were no lessons on Sunday.

On Monday morning, Gupta said "approximately 80% of the debris had been cleared" from the building, and "only the rubble from the basement remains".

The BBC found the area around the site of the collapse cordoned off and teeming with rescue workers in bright orange uniforms.

An excavator dug through the rubble in the hope of finding survivors amidst a pile of bricks. In another corner, a few mattresses half covered in debris were lying in a pile.

The smell of burning metal was overpowering as teams of the National Disaster Response Force (NDRF) could be seen using electric saws to cut through iron grills, penetrating layers and layers of steel and concrete.

There is no confirmation if there are still people under the debris or if there are more survivors.

Hospital officials are not saying whether the casualties include students, local residents or labourers who were working in the basement.

On Sunday,a local legislative assembly member at the scene said that some of the trapped students had been making calls from under the rubble.

An eyewitness who was at his shop nearby when the tragedy struck told news agency ANI that the building collapse sounded "like the rumble of an earthquake".

"We rushed out immediately; there was a lot of smoke and dust here. The entire building had collapsed. Some bodies were recovered, and they also rescued four students who were still breathing."

He said he could hear students crying out from under the rubble saying "save us, save us!"

Gupta said an adjacent building had been evacuated "as a precautionary measure" -and local media reports say it would be demolished on Monday.

"Every possible effort is being made to safely rescue those trapped," she added.

Delhi Police said the building had only been 40 or 50 years old.

The owner of a nearby shop told ANI that it had been under a 100-year lease and that the leaseholder had undertaken excavation work in the basement to expand the hostel and increase their income.

A civic official said they were trying to ascertain whether any digging or structural work was carried out in the building recently, Times of India reported.

"Given the incessant rain, we are examining the possibility of seepage weakening the structure. Repair or other work could also have contributed to the collapse. At this stage, however, it is difficult to establish the exact cause," he said.

Police have registered a case against the owner of the building and are searching for him.

The National Students' Union of India called on the government to investigate the cause of the collapse and hold anyone found responsible to account.

"Negligence with the safety of students and common people will not be tolerated at any cost," it said.

Satya Niketan is a densely populated area which houses a large student population, with a number of hostels in the neighbourhood.

Many students who come from outside Delhi to attend South Campus colleges are forced to live in cheap private hostels and paying-guest (PG) accommodations due to a lack of hostel facilities on campus.

"There are 75 students in Sociology Honours class, but only two get a seat in the college hostel. All other students have to live here," Sawai Sharma, a student of Venkateswara College, told BBC News Hindi.

Sharma, who often visited a friend who lived in the building and narrowly escaped the accident, said a bed in the building cost 18,000 rupees ($190; £140) a month, making it affordable for students.

Another student, Shivam Yadav, said a friend of his lived in the building and was in his room at the time of the accident.

"He was on the third floor at the time of the accident. He has been rescued and sent to hospital."

Yadav said that most of the buildings in Satya Niketan are "overloaded".

"The buildings are in a dilapidated condition. No inspections are conducted. There are no rules or guidelines here."

College student Ankit Tiwari said conditions at these hostels and PGs "are appalling".

"Students are paying a lot for a very small space which they share with others. There is no proper water or sewage facility here."

Tiwari, who lives nearby, reached the site about half an hour after the collapse. "Students were helping each other as we came first, before the rescue teams arrived. What we saw was tragic. We have been finding books, mangled desks and study notes," he said.

Building collapses are relatively common in Delhi, with more than a thousand recorded in the past three years causing dozens of deaths, according to fire department figures.

Poor foundations, inadequate materials and unqualified construction workers were among the common reasons for collapses.

Eleven people, including three children, were reportedly killed last April when a residential building collapsed in north-eastern Delhi.

In 2024, three students drowned after getting trapped in the flooded basement of an exam coaching centre in capital Delhi, sparking anger and protests.