A nearly 50-year-old five-storey building housing a boys' hostel in Satya Niketan near Delhi University's South Campus collapsed on Sunday afternoon, killing five people and leaving four others undergoing treatment at AIIMS Trauma Centre, police said. One of the injured has undergone limb surgery.The building, known as 'Hostel Daze', comprised a basement and five upper floors and was being used as a paying guest (PG) accommodation. Repair work was underway in the basement when the structure collapsed at around 1:30 pm, a senior officer said.Two teams of the National Disaster Response Force (NDRF), comprising around 70 personnel and a canine squad, have been deployed for the rescue operation. Oxygen cylinders were dropped under the rubble to help those trapped breathe, an NDRF officer said. Fire tenders and police teams have also been stationed at the site.Also Read: South Delhi building collapse: People trapped under debris calling on phones for helpLocals claimed that 40 to 50 people could still be trapped under the debris, but Delhi Police said the exact number of people trapped or injured was not known.The densely packed area has narrow lanes lined with eateries and PG accommodations catering mainly to students. Residents joined rescue teams in the search for people trapped under the debris, using their hands and tools to clear the rubble.Visuals of the building collapsed in Delhi's Satya Niketan area— ANI (@ANI) The fire department received an alert around 1:30 pm, following which eight fire tenders and police teams were rushed to the spot. Paramilitary personnel were deployed to ensure unobstructed movement of ambulances.Rescue operation underwayDelhi Chief Minister Rekha Gupta, Lieutenant Governor Taranjeet Singh Sandhu, Police Commissioner Anurag Kumar and BJP MP Bansuri Swaraj visited the site following the collapse.The Joint Commissioner of Police, New Delhi Range, DCP Southwest and Additional DCP are supervising the rescue operation, an officer said.Delhi Police said the process to register an FIR was underway and seven to eight teams were searching for the building's owner, who is based in Gurugram."The exact number of persons trapped/injured is still not known at present. Further details will be shared as and when confirmed," Delhi Police said in a statement.The authorities have also advised locals and onlookers to stay away from the site.Rain, basement work under scannerRepair work was underway in the basement before the building collapsed. Locals claimed that water had accumulated in the basement following days of rain and may have weakened the building's foundation.Also Read: 'Students forced to live in unsafe PGs': Opposition slams govt over Delhi building collapseAn eyewitness also said construction work was being carried out in the basement and claimed that the foundation and lower pillars were weak. Police sources confirmed that construction work in the basement was ongoing before the incident.Delhi has witnessed incessant rain since Friday.Residents have also raised concerns about the condition and maintenance of other buildings in the area, where several residential properties have been converted into PG accommodations.A local resident said many buildings in the area have been extended to five or six floors and alleged that maintenance was not carried out regularly.— ANI (@ANI) Students among those staying at PGThe building housed around 15 rooms, with two to three students sharing each room, according to local resident Rajen Chhetri, who works with the Delhi Police.He said many students staying in the locality were from Kerala, Haryana and Uttar Pradesh and studied at nearby colleges, including Motilal Nehru College, Atma Ram Sanatan Dharm College and Sri Venkateswara College. Students were paying around Rs 12,000 per bed, he said.Also Read: ABVP members detained for protesting over Satya Niketan building collapse at MCD headquartersBJP MLA Anil Sharma, who visited the site, said some calls had been received from people believed to be trapped inside the debris.An eyewitness said the tragedy could have been worse had it occurred on a working day, as many students had returned home for the weekend.PM Modi, Shah express griefPrime Minister Narendra Modi expressed condolences to the families of those who lost their loved ones and prayed for the speedy recovery of those injured."The collapse of a building at Satya Niketan, Delhi is distressing. Condolences to those who lost their loved ones. Praying for the speedy recovery of the injured. Authorities are working at the site and assisting those affected in the mishap," Modi said in a post on X.Also Read: PM Modi condoles deaths in Delhi building collapse, prays for speedy recovery of injuredUnion Home Minister Amit Shah also expressed grief over the deaths and said he spoke to the Delhi chief minister, police commissioner and the NDRF director general to assess the situation."The injured are being provided with all necessary medical assistance. Praying for the speedy recovery of all those injured," Shah said on X.Union Health Minister J P Nadda also spoke to Gupta and offered assistance, official sources said.Rahul Gandhi expresses concernCongress leader Rahul Gandhi described the building collapse as "extremely heartbreaking and alarming", saying reports indicated that several people, including Delhi University students, were trapped under the debris.He appealed to the NDRF, Delhi Fire Service and other rescue teams to make every possible effort to reach those trapped and ensure that the injured receive immediate and the best possible medical treatment.Gandhi said Congress and NSUI workers were present at the site and ready to provide assistance, adding that the party stood with the victims and their families.He also raised concerns over the shortage of adequate hostels in colleges and universities, saying students are forced to live in PG accommodations in "inhumane conditions". Gandhi said every student's life was precious and their safety must be ensured under all circumstances.